There were signs yesterday of bitterness among Conservatives at Gordon Brown’s decision to invite Baroness Thatcher to Downing Street for tea.

Rob Wilson, a frontbencher, claimed that Lady Thatcher was lonely, frail and losing her memory and accused Mr Brown of using her in a “shallow, self-serving and unscrupulous way”. Gerald Howarth, a defence spokesman who served as a parliamentary aide to the former Prime Minister, similarly accused Mr Brown of manipulating her as her health declined.

But such criticisms were dismissed by Lady Thatcher’s circle. Mr Brown’s aides, too, leapt to her defence, describing the comments as hurtful and unfair and demanding an apology on her behalf.

The row was prompted by an article by Mr Wilson on the website ConservativeHome.com, in which he voiced deep unease at Thursday’s meeting between Mr Brown and Lady Thatcher, suggesting that she had been tricked into a cynical publicity stunt.

“Baroness Thatcher is 81, she is elderly, she is lonely, she is frail and she has difficulty with her memory,” he wrote. “Those closest to her say that her grasp on daily life is ‘some days better than others’. She would naturally have been flattered by an invitation to Downing Street and would have enjoyed being back in the thick of the political action.

“I put to you the following questions: is it right that a serving prime minister should exploit a situation like this for his own political ends? Is that what Gordon Brown did yesterday? Was this another carefully choreographed Brown ‘dog-whistle’ to Conservative-minded electors that it’s ‘safe’ to vote for him?”

He was supported by Mr Howarth, one of the Tory MPs closest to Lady Thatcher who served as her private parliamentary secretary in the Commons in 1991-92, just after she left Downing Street. “Everyone knows that she is not in the same rude health she was a few years ago, but I personally believe that this Prime Minister is every bit as manipulative as the previous one,” Mr Howarth said.

“For a man who has spent his whole political life castigating the Conservatives, I find this nauseating to see him trying to cash in on the public affection for Lady Thatcher. I despise utterly the Prime Minister’s motives. I’m also of the view that if a former prime minister is invited [to No 10] by a current prime minister, it is inconceivable that she would turn it down. She is a courteous person.”

The comments provoked an angry response from Lady Thatcher’s spokesman. He said that Mr Wilson’s description of her was inaccurate and rejected the notion that she was exploited. He told The Times: “It is nonsense to suggest that the Prime Minister was just trying to use her. It was very courteous to invite her and very kind to invite her. It is Prime Minister to Prime Minister and the politics does not come into it. I just don’t think it is terribly helpful. She still leads a very active life.”

Lady Thatcher was invited back to No 10 by both Tony Blair and John Major, and similarly invited her own predecessors, he said. “It is a natural thing for a prime minister to do. It was very nice for her to be back and it brought back a lot of memories.”

Sources close to Mr Brown accused Mr Wilson, the Conservatives’ higher education spokesman, of seeking to “denigrate” Lady Thatcher. One said: “Mr Wilson’s account of his meeting with Lady Thatcher is hurtful and unfair, and it does not match in any way with the Prime Minister’s private meeting with her.

“No matter whether they agreed or disagreed with her policies, Lady Thatcher is respected by millions of people in Britain as a strong leader who still holds strong views on the future of the country. It is disappointing that Mr Wilson has chosen to denigrate her in this way and he should apologise.”

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