Conservative Prime Minister David Cameron has promised to renegotiate Britain's ties with the EU and then, by the end of 2017, hold a referendum on whether to stay in or leave.

Under the government's initial proposal, voters were to be asked to say "yes" or "no" to the question "Should the United Kingdom remain a member of the European Union?"

Some who want Britain to leave the 28-member bloc said that was unfair as it would allow the campaign to stay in to brand itself as the more positive "yes" camp.

"Whilst voters understood the question in the bill, some campaigners and members of the public feel the wording is not balanced and there was a perception of bias," saidJenny Watson, chair of the Electoral Commission.

Following a public consultation, the commission recommended the question be changed to: "Should the United Kingdom remain a member of the European Union or leave the European Union?" The two possible answers would be: "remain a member of the European Union" and "leave the European Union".

A spokeswoman for Cameron said the government would follow the commission's advice and amend the legislative bill.

"The prime minister's objective has always been very clear, to give people a simple, clear choice, and we believe that will still be achieved with the recommendation from the Electoral Commission today," she told reporters at a regular briefing.

In last year's referendum on Scottish independence, the phrasing of the question was such that those in favour of independence had to answer "yes" while those who wanted to stay in the United Kingdom had to answer "no".

This led to misgivings among some in the "no" camp that it made their campaign sound too negative, although in the event a majority of voters did opt for "no".