British opposition politicians demanded an apology from Prime Minister Gordon Brown today after the resignation of a top adviser said to have sent emails suggesting a gossip campaign about opposition Conservatives, Reuters reported. Damian McBride, who was head of strategy and planning in Brown's Downing Street office, proposed in one email a "campaign of unfounded personal slurs" against senior Conservatives and their wives in an attempt to embarrass the opposition as an election approaches, the Sunday Times newspaper said. Senior Conservative lawmaker William Hague told Sky News: "We do want a clear apology from the prime minister himself." "It's very important that he shows personally that he takes this very seriously and gives his assurance that this sort of thing is not going to happen again," he added. "If that is not an orchestrated dirty tricks campaign, I don't know what is," added Conservative legislator Chris Grayling, speaking to the BBC. Conservative lawmaker Nadine Dorries, who was mentioned in emails she described as false and libellous, said she was seeking legal advice. The Conservatives, keen to play up the impression of a government in disarray as a general election looms within the next 14 months, have stepped up their attacks on Brown.