Last week's tragedy at Virginia Tech University, in which a crazed South Korean gunman, Cho Seung-Hu, killed 32 people in cold blood, has once again sparked a debate on gun control in America. The United States has witnessed at least 19 fatal school shootings in the last decade; the most recent one was in Pennsylvania last October, when a milkman killed five girls in an Amish village school.

Gun control is an extremely divisive and passionate issue in the United States and the National Rifle Association (NRA), the country's main gun lobby, is probably the single most powerful political action committee in America. The NRA, which says its has 4.3 million members and a $180 million annual budget, argues that gun ownership is a civil liberty protected by the Second Amendment of the US Constitution.

Opinion polls consistently show that a majority of the American public would support stricter gun controls and a Gallup poll last year showed a 56 per cent majority in favour of such controls. However, the question of gun control is almost taboo within American political circles, and this just shows what powerful a lobby the NRA is.

Polls also show that there is a strong urban/rural/regional divide on this question. While voters living in large cities or coastal areas tend to favour stricter gun controls, those in America's heartlands or in rural areas oppose them.

There are as many as 80 million gun owners in America, all of whom believe that the right to bear arms is a cherished constitutional right which should be defended at all costs. The NRA goes through extraordinary lengths to ensure that gun control is not placed on the political agenda. It also often funds congressional candidates who are anti-gun control and targets pro-gun control candidates for defeat.

In the 1994 congressional election, for example, the NRA is credited with defeating Congressmen Jack Brooks and Tom Foley, the first Speaker of the House to lose a re-election since 1860. Bill Clinton wrote in My Life, his autobiography (pages 629-30):

"The NRA had a great night. They beat both Speaker Tom Foley and Jack Brooks, two of the ablest members of Congress, who had warned me this would happen. Foley was the first Speaker to be defeated in more than a century. Jack Brooks had supported the NRA for years and had led the fight against the assault weapons ban in the House, but as chairman of the Judiciary Committee he had voted for the overall crime bill even after the ban was put into it. The NRA was an unforgiving master: one strike and you're out. The gun lobby claimed to have defeated 19 of the 24 members on its hit list. They did at least that much damage and could rightly claim to have made Gingrich the House Speaker."

In Congress, the Democrats, who today control both the House of Representatives and the Senate, and who have attacked the Bush administration over a wide range of issues, have remained largely silent on gun control. The reason? Opinion polls show that gun control puts voters off in rural swing states - which narrowly voted for George Bush in 2000 - and with a presidential election next year, it would be better to sideline this issue.

The NRA's close links with President Bush and many Republicans are very evident. Before the 2000 election it boasted that it was so close to George Bush that it would "work out of his office". Furthermore, NRA support for the Republicans has been rewarded by the Bush administration with a series of measures aimed at strengthening the rights of gun owners and manufacturers. One such measure was a White House order for the FBI to destroy records of background checks on gun owners within 24 hours, amid NRA concerns that the information would be used to create a national gun registry.

Ironically, the three leading Republican presidential candidates - John McCain, Rudy Giuliani and Mitt Romney - are all broadly in support of stricter gun control. It will be very interesting to see how the NRA will deal with a pro-gun control Republican presidential candidate.

The NRA has also sought to build bridges with the Democrats. Howard Dean, the party's chairman, has argued that gun control policy should be decided at state level. This resulted in the election of a number of anti-gun control Democrats in rural states last November, many of whom were actually backed by the NRA, which further weakened the party's traditional pro-gun control credentials. The NRA's percentage of funding going to Democrats also increased from six per cent in 2002 to 13 per cent last November. The rest of the funding, of course, went to friendly Republicans.

A day after the Virginia Tech shootings, President Bush took part in a memorial service on campus for the victims. He told grieving students, academics and relatives of those killed that the victims found themselves in the wrong place at the wrong time. Mr Bush gave a very dignified speech - America is always at its best when it grieves and remembers. There was, however, no reference (not surprisingly) to the country's gun culture; nor was there any mention of possible new gun control measures.

America needs some thorough soul-searching over gun control which will produce legislation to make the country - and the country's schools and universities - safer. Perhaps if the gun shop owner in Virginia had been obliged to conduct a meticulous background check and seek references before selling Cho Seung-Hu a gun, he might have discovered what his professor Lucinda Roy knew from his writings: that he was a deeply disturbed individual who fantasised about shooting people.