All official records of MPs’ expenses from the scandal-hit era before 2010 have now been destroyed by the Commons authorities, it has emerged.

The disposal of the records was revealed in a letter to Conservative activists who made a complaint about the expenses of their local MP relating to claims between 2004 and 2010.

According to the Telegraph, Kathryn Hudson, the standards commissioner, wrote back saying: “All records relating to expenses claims before 2010 have now been destroyed. No unredacted information is now available here nor any notes of conversations or advice given … which might establish the facts.”

The destruction of the records means there is no longer any chance of the investigating authorities reviving old cases such as Maria Miller’s mortgage claims, which led to her resignation as culture secretary. It means the only unredacted copies of MPs’ claims from that era are held by the Telegraph, which broke the expenses scandal in 2009 and led to a public outcry that saw many MPs losing their seats.

A House of Commons spokesman said the policy on destroying MPs’ expenses records was longstanding and to comply with data law.

It was originally set by the Commons members’ estimate committee, which is now chaired by John Bercow, the Speaker of the house.

“Destruction dates for records are prescribed by the House of Commons authorised records disposal practice (ARDP) policy, and in compliance with the Data Protection Act,” a statement from the Commons said.

“The retention period for general financial data, of which members’ expenses is a subset, is three years after the current financial year finishes. The longstanding policy on retention of MPs’ expenses records was originally agreed by the members estimate committee (MEC).

“In accordance with the ARDP, the disposal of records relating to members’ expenses claims pre-2010 was carried out on a routine basis at various times each year up to 2014, four years after the House of Commons’ oversight of the MPs’ expenses arrangements finished.”

Sir Alistair Graham, the former chairman of the committee on standards in public life, told the newspaper that historians have been denied the chance to study parliament’s “worst hour”.

“It is scandalous that anybody has destroyed the records for that period. Who knows what anybody’s motivation was?

“The people concerned should know better. There was a strong public interest in retaining this information so that people have access to it, and I’m really very surprised.”