As the chances of Mr Brown surviving faded after the decision of the Work and Pensions Secretary to time the announcement of his departure as polls forEuropean and local elections closed, the monarch will now consult her most senior advisers if Mr Brown loses his fight to stay in office.
While the Queen still technically has the power to dissolve Parliament, in reality she only advises her prime ministers. It would be unprecedented for a second prime minister to move into 10 Downing Street without a general election.
A number of senior constitutionalists approached by The Daily Telegraph said they hoped the Queen would exercise her right to propose to Mr Brown's successor that he or she secures an early public mandate. Even though the main Opposition parties would lead the clamour for a poll by autumn at the latest, a new prime minister could ignore them.
Vernon Bogdanor, Professor of Government at the University of Oxford, said: "There would be considerable public pressure for an early general election if there is another unelected prime minister.
"The Queen can suggest, or advise or warn the next Prime Minister that it would be a good idea to seek an early mandate."
After James Callaghan replaced Harold Wilson in 1976 and when Margaret Thatcher resigned in 1990 there was little public pressure for an election. When Mr Brown took power in June 2007 there were limited calls for an immediate election.
Prof Bogdanor said: "The public attitude has changed. Most people would say if Brown is toppled, particularly in the current circumstances, there would have to be an early poll, which I imagine most Labour MPs would not want."
He also said that if Mr Brown continued to ignore clear signs that he had lost the support of the Parliamentary party and the Cabinet the Queen would have a constitutional role. "If he cannot form a Cabinet, or appears to have lost the support of a large number of MPs, the Queen can ask the Prime Minister if he thinks it is in the best interests of the government and the country if he should continue. It is an advisory role. No more. It is what she is restricted to."
Another constitutional adviser, who declined to be named, said: "I am sure the Queen, who is always well advised on these matters, would think it appropriate at the very least for a public time table to be set by Gordon Brown's successor if there is to be one."
After James Callaghan replaced Harold Wilson in 1976 and when Margaret Thatcher resigned in 1990 there was little public pressure for a general election. When Gordon Brown took over from Tony Blair in June 2007 there were limited calls for an immediate election.
Professor Bogdanor said: "I think the public attitude has now changed. Most people would say if Brown is toppled, particularly in the current circumstances, there would have to be an early poll which I imagine most Labour MPs would not want."
Buckingham Palace declined to be drawn on whether the Queen had discussed the position with her advisers or would exercise her right to make the case for an early poll. A spokeswoman said: "We can never confirm, deny or discuss any discussions that take place between the Queen and her advisers."
