The long premiership of Britain's Tony Blair is nearing its end. Only 16 months after Mr Blair's historic third electoral victory - something the Labour Party would never have imagined possible in the past - Labour seemed to be sliding into open warfare over the Prime Minister's departure with some MPs demanding he announce his exit date immediately.

Mr Blair did not give his departure date but did announce he would be gone within the next 12 months, paving the way for Chancellor Gordon Brown to take over, that is, if the party decides to elect him as Mr Blair's successor. The fact that Mr Blair felt compelled to say that he would go within a year - as a result of pressure by rebel MPs, who included six parliamentary private secretaries and a junior minister, all of whom resigned - shows that this was a serious rebellion within the party.

Mr Blair was right to apologise to the nation on behalf of the Labour Party for its somewhat shabby behaviour, saying it certainly was not the party's 'finest hour'. The Prime Minister had already made it clear that he would not contest the next general election as party leader and there has been speculation ever since about just when he would depart.

It is still not clear whether these Labour rebels - some of whom were considered to be Blairites - had the backing of Gordon Brown. The Chancellor has in fact denied any involvement in the plot but he only spoke out against the MPs after it was clear that Mr Blair was not going to give a precise exit date.

It seems strange to some observers why a number of Labour MPs would want to push for Mr Blair's early exit from the political stage. He is, after all, the most successful Labour Prime Minister in British political history, having led the party to three consecutive electoral victories, the first two being landslide victories, and who crucially managed to capture the centre ground in British politics.

On the whole I think it is fair to say that Mr Blair has been a good Prime Minister who presided over a very strong economy, job creation, important educational, welfare and health reforms, political reform and a more internationalist foreign policy. Of course he has made mistakes - Iraq is clearly one of them - and he has had limited success in improving public services - but it is important to look at the whole picture when judging someone.

There are a number of reasons why some of his backbenchers - and indeed some of his own ministers - want Mr Blair to go. First of all some of them are simply supporters of Mr Brown and believe that it is time for a change at the top. They may - or may not - have policy differences with Mr Blair but feel that the Prime Minister's time is up and that only Mr Brown can save the Labour Party from defeat at the next election in three years' time. They say the party's very poor performance at the last local elections as well as in the opinion polls is enough reason for Mr Blair to go.

Then of course there are those left-wing Labour MPs who have nothing in common with Mr Blair and who oppose him on ideological grounds. These MPs have voted against their government in areas such as social security, health and education. They despise Mr Blair's pro-American foreign policy as well as his market-driven agenda and his involvement of the private sector in the health and educational sectors. They would like nothing better than to see Mr Blair depart immediately.

Iraq, of course, is another main reason why many in Mr Blair's party would like him to go and this has little to do with the left-right divide or the Brown-Blair dispute. It is true that the left-wingers as well as many of the Brownites are citing Iraq as a reason why Mr Blair should resign but you don't have to be in either of these camps to realise that Iraq has been a disaster and could prove to be a huge liability to the party at the next general election.

Furthermore, Mr Blair's recent reluctance to push for an early ceasefire in the conflict in Lebanon between Israel and Hizbollah made many Labour MPs very uncomfortable, especially those whose constituencies include many Muslim voters.

So should Mr Blair have set an exact departure date instead of simply saying that he will step down within 12 months? In May 2007 he would have served as Prime Minister for 10 years, quite an achievement and a good time to go. Perhaps, however, he should soon announce his exit date, whether this is to be in May or before. This will allow some time for an open and honest debate among the leadership contenders - there are bound to be some Labour heavyweights who will challenge Mr Brown - which is what the British people deserve.

There is no doubt that Gordon Brown is one of the most intellectually formidable politicians of the post-war era but the electorate have a right to know exactly where he stands on key issues. As Chancellor over the past nine years he must take some of the credit for Britain's strong economy. However, is he as committed as Mr Blair to market-oriented reforms vis-à-vis public services? And where exactly does he stand over Europe and relations with the United States? Will he differ, if at all, from Mr Blair's foreign policy? And, perhaps most importantly, is he the best man to beat the Conservative Party leader, David Cameron?

Mr Blair has said he still has important educational and health reforms to carry out. Setting an exact departure date would perhaps create some sympathy for the Prime Minister. Who, after all, would want to vote against their own departing leader? So perhaps this would be the best way for Mr Blair to ensure that his final pieces of legislation are passed by Parliament and to exit in a grand style.

The most important thing for the Labour Party is that they remain a united party and do not challenge Mr Blair's authority any further. The electorate hates weak governments and divided parties. Look at what happened to the Conservatives under John Major in 1997. Just before that election Mr Blair had said Mr Major was "weak, weak, weak", adding: "I lead my party. He follows it." I hope Mr Blair won't come to regret those words.