Britain and France talked about a "union" in the 1950s, even discussing the possibility of the Queen becoming the French head of state, it was reported today.

On September 10 1956, Guy Mollet, the then French prime minister, came to London to discuss the possibility of a merger between the two countries with his British counterpart, Sir Anthony Eden, according to declassified papers from the National Archives, uncovered by the BBC.

A British cabinet paper from the period reads: "When the French prime minister, Monsieur Mollet, was recently in London, he raised with the prime minister the possibility of a union between the United Kingdom and France."

At the time of the proposal, France was in economic difficulties and faced the escalating Suez crisis. Britain had been a staunch French ally during the two world wars.

When Mr Mollet's request for a union failed, he quickly responded with another plan - that France be allowed to join the British commonwealth - which was said to have been met more warmly by Sir Anthony.

A document dated September 28 1956 records a conversation between the prime minister and his cabinet secretary, Sir Norman Brook, saying:

"The PM told him [Brook] on the telephone that he thought, in the light of his talks with the French:

· That we should give immediate consideration to France joining the Commonwealth

· That Monsieur Mollet had not thought there need be difficulty over France accepting the headship of her Majesty

· That the French would welcome a common citizenship arrangement on the Irish basis."

However, this proposal was also eventually rejected and, a year later, France signed the Treaty of Rome with Germany and the other founding nations of the European common market.

"I tell you the truth - when I read that I am quite astonished," the French Nationalist MP, Jacques Myard, told the BBC today.

"I had a good opinion of Mr Mollet before. I think I am going to revise that opinion. I am just amazed at reading this, because since the days I was learning history as a student I have never heard of this. It is not in the textbooks."

No French record of the proposal appears to exist, and it is unclear whether there were any proposals for the name of the new union.

A spokesman for the French embassy said most people had been surprised by the revelation. "We are looking at our national archives," he said. "We cannot comment at this stage."

The idea of a link-up between countries was not unique. Between 1958 and 1961, Egypt and Syria merged to become the United Arab Republic in an initial move to establish a pan-Arab state.

The union broke up following a coup in Syria, but Egypt continued to call itself the United Arab Republic until 1971.

The BBC's Document programme will broadcast an edition on the proposed merger, called An Unlikely Marriage, at 8pm tonight on Radio 4.