John Major’s planned tribute to the Queen’s “priceless” contribution to the UK on the 40th anniversary of her accession to the throne was changed by his aides, who feared the word might not be seen as appropriate given her tax-exempt status at the time, papers released at the National Archives reveal.

The then British prime minister wanted to send the cabinet’s “warmest good wishes” in “recognition of the priceless contribution her majesty has made to the life of our nation throughout her reign”.

However, on a draft of the wording, the then No 10 private secretary, William Chapman, circled the word “priceless” and asked Major’s principal private secretary, Andrew Turnbull: “Is this quite the mot juste [appropriate word]? In view of the Queen’s tax exemption, it could indeed be said that her contribution has been price less”.

Chapman continued: “Cheap at the price, I would have said. How about ‘unique’, ‘unparalleled’, or a new phrase altogether, ‘incomparable part which HM has played in…’”

Turnbull’s reply, in a note on the same draft released by the archives in Kew, south-west London, read: “It was the PM’s choice, but I am open to suggestion based on your long and expensive education in the English language.”

Discussion over the wording took place in January 1992, ahead of the anniversary in February. The announcement that the Queen was volunteering to pay tax was not made until November 1992. It followed public pressure over the cost of the monarchy and questions as to who would pay the bill for repairing Windsor Castle, which was severely damaged by a fire that month.

The Queen and the former prime minister Margaret Thatcher had agreed the 40th anniversary would be low-key, not on a par with her 25th. The palace had let it be known that any humble address – a communication from the House of Commons to the monarch – by a delegation of parliamentarians would not be favoured.

However, Major felt a cabinet tribute was in order, and in a handwritten note on two alternative forms of wording, he suggested the word “priceless”.

The cabinet tribute was pronounced in prime minister’s questions, though at one stage, there were concerns that the then Labour leader, Neil Kinnock, might not be agreeable to this mechanism because “he feels that question time is currently too partisan to admit such lofty sentiment”, Turnbull wrote in a note to the then prime minister.

Eventually, it was agreed, and Major delivered the phrase “in recognition of the incomparable contribution your majesty has made to the life of our nation throughout your reign”.