Leading tobacco companies vehemently denied allegations by Mr Streeter that they used advertising indiscriminately, or to target children in developing countries.

 The shadow international development secretary made the claim in a letter to BAT in which he urged the company to extend to every country Britain's code of practice on cigarette advertising. Mr Streeter said in his letter that the landscape of many African countries was "plastered with new and aggressive billboards promoting cigarettes, many of them your products, often sited where children play and often carrying no health warnings".

 The move had the backing of William Hague and Liam Fox, the shadow health secretary, but infuriated some Tory MPs and provoked hints that the tobacco industry would look less favourably on the Conservatives in future.

 John Carlisle, spokesman for the Tobacco Manufacturers' Association and a former Tory MP, accused Mr Streeter of making "unsubstantiated accusations". Asked whether the incident might jeopardise support from the industry for the Tories, Mr Carlisle told The World at One on BBC Radio 4: "We will support any political party if they give us a fair and balanced argument, and that certainly has been the case with the Conservative Party over the last few years.What we don't want is unsubstantiated accusations without consultation beforehand. We don't want to be accused of targeting children because we do not." A lot of Tories were "bristling" at Mr Streeter's remarks, Mr Carlisle said.

 Mr Clarke said he rejected Mr Streeter's complaint. "They are based on mistaken allegations that we aim our advertising at children. BAT has not, does not and will not target children." He had seen advertisements for at least one of BAT's brands, Sportsman, during a recent holiday in Uganda, one of the countries on which Mr Streeter had based his claim. "It shows a picture of a jockey. It doesn't seem to me to be aimed at children at all."

 Simon Millson, a spokesman for BAT, said the company had consistently said that the minimum legal age for buying cigarettes should be raised from 16 to 18, but that advice had been ignored by successive governments.

 Gallaher, Britain's largest tobacco company, Imperial Tobacco, also British, and Philip Morris, the American group, all said that they complied fully with regulations imposed by the country in which advertisements were sited. None of the companies would disclose how much they spent annually on cigarette advertising.

 Labour accused the Conservatives of hypocrisy and described Mr Streeter's letter as a "a joke". Tessa Jowell, the Minister for Public Health, said the Tories continued to oppose any rise in tobacco duty and had no serious policy on smoking. "If the Tories really cared about the lives of smokers outside the UK they would not have blocked a ban on tobacco advertising and sponsorship for years at European level. It is only with Labour that a ban has been introduced."

 Mr Streeter first considered raising the issue last December after visiting Nigeria. The trip, one of four he has made to Africa since he was appointed shadow international development secretary last year, alerted him to what he said was widespread and indiscriminate cigarette advertising without health warnings. Urging companies to act responsibly was "a very Conservative thing to do", he said.