John McCain, the presumptive Republican presidential nominee, fiercely rejected a newspaper report that romantically linked him to a 40-year-old female political lobbyist and accused of granting her clients political favours.

Mr McCain, 71, had denied the claims to the New York Times but, after sitting on the story for several weeks, the paper published them.

The piece claimed that, eight years ago during his first run for the White House, his aides were so concerned about his relationship with Vicki Iseman that they blocked her access to him to "protect the candidate from himself".

Mr McCain and Ms Iseman both denied to the newspaper that they had ever had a romantic relationship. The story was first alluded to on the Drudge Report website just before the Iowa and New Hampshire nomination contests, but after frantic lobbying by Mr McCain and his aides at the time the New York Times did not publish it then.

A race like a crackpot Dynasty

The contest between Barack Obama and Hillary Clinton matches any fiction

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It was unclear last night what impact the allegations would have on Mr McCain, who is now on the verge of wrapping up the Republican nomination after staging an extraordinary political comeback. He had been written off in the presidential race six months ago when his campaign collapsed.

The timing of the allegations comes as Mr McCain had begun to build bridges with his party's conservative base and as the Republican establishment have rallied behind him in anticipation of a general election fight against either Hillary Clinton or Barack Obama.

The potentially most damaging allegations contained in the article centre on Mr McCain's reported conflicts of interests in the areas of political funding and lobbying. He has built a reputation as a scourge of the excesses of both but is accused of several instances of hypocrisy.

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