Robert Key, one of Mr Portillo's former ministerial colleagues, publicly criticised Mr Gummer for not backing the Secretary of State for Defence in a recent row about the possible sale of the historic Admiralty Arch in London.
The renewed in-fighting follows a week of bitter internal strife in the Conservative Party during which Baroness Thatcher issued a damaging rallying call to the right.
Mr Portillo claimed in a radio interview last week that left-wingers were plotting against him. His allies argued that it was too much of a coincidence that hostile news stories concerning Admiralty Arch appeared while Mr Portillo was out of the country. These included quotes from the former Admiral of the Fleet, Lord Hill-Norton, who described Mr Portillo as "a little creep".
Mr Key said the disposal of Admiralty Arch was the responsibility of the Department of the Environment, where Mr Gummer is Secretary of State. He said: "The Department of the Environment should have been ready to put its hand up and explain what the true position was. It didn't.
"I did not notice the Secretary of State speaking out to defend a Cabinet colleague who was on the other side of the world." Mr Major later intervened to rule out the Admiralty Arch sale.
Mr Key, who has served at the Department of the Environment, said he did not believe in conspiracies. But he argued that a number of individual cliques were targeting Mr Portillo. His run of poor publicity was more than a coincidence, he said.
Mr Key's letter to the Prime Minister drew attention to "a number of incidents", blaming elements within the party but naming no individuals.
Mr Gummer, who is thought to have been angered by the accusation, said, through a spokesman: "Such an allegation would be total fiction. The opposite is true. Mr Gummer was on holiday and spent a great deal of time doing his best to ensure that the incorrect conclusion drawn by the story was put right".
His allies say the original press article arose out of a briefing from the Ministry of Defence.
Mr Key has not received a reply from Mr Major, but has been assured by the Chief Whip that Downing Street and Conservative Central Office are not pursuing any vendetta against Mr Portillo.
This latest row comes amid signs that Mr Major will offer an olive branch to the pro-Europeans - by refusing Eurosceptic demands for a White Paper detailing Britain's negotiating position ahead of the forthcoming European Inter-governmental Conference.
Mr Major is said to have received "dozens" of letters from pro-Europeans calling on the Government not to lock itself into a negotiating position. Peter Temple-Morris, a leading member of the Macleod group of One-Nation Tories, said: "I have no hesitation in saying there should not be a White Paper before we go into a most important set of international negotiations.
"It is unheard of to tie yourself into a position before you enter a major international negotiation, because it indicates that you are not going to negotiate - and that would be harmful to our interests."
The ex-Cabinet minister and leading Eurosceptic John Redwood may, however, fill the void by publishing his own version of a white paper. It would rule out any extension of qualified majority voting or increased powers for the European Parliament, as well as setting out firm opposition to a single European currency.
The Conservative Party chairman, Brian Mawhinney, ignored the internal Tory battles to concentrate yesterday on criticising Tony Blair's vision of a "stakeholder economy". He said that a future Labour government would sell out to the trade unions and Brussels.
In a speech in his Peterborough constituency, Mr Mawhinney said the Labour leader was trying to sell "second-hand socialist policies wrapped up in Tory ribbons".
Commentary, page 19
MOST of his political enemies Michael Portillo can probably do without. Certainly, he claims that he is a minister much maligned. But the Secretary of State for Defence will probably be grateful for the latest assault on his reputation. The North Koreans yesterday gave him a verbal lashing, accusing him of being "reckless" and "bellicose", and whipping up "war fever".
On a trip to South Korea this month, Mr Portillo said there was a rising threat from the North's hardline Communist regime, and spoke of the "unpredictability" of the regime in Pyongyang. Mr Portillo said it was vital to ensure that "the deterrent is not in any way in doubt".
The official North Korean news agency had a clear-cut analysis of his views. His comments "revealed that he is only a servant of munitions monopolies which want to increase arms sales to South Korea, in return for rendering the situation of this region strained". It claimed "bellicose elements of the British military" had been "embroiled in reckless acts" of aggravation. "Our people and army are keeping a close eye on the British military, whipping up war fever in the Korean peninsula."Reuse content