Lord Hanningfield was barred in May after the standards watchdog found he claimed a daily £300 Lords attendance allowance on 11 days when he did not "undertake any parliamentary work".
It came after a Daily Mirror investigation into the former Essex Council leader's journeys to the Lords.
A man, believed to be the peer, has been interviewed under caution.
The Lords Commissioner for Standards, the former Hampshire Chief Constable Paul Kernaghan, investigated Lord Hanningfield's expenses following the newspaper report.
The Daily Mirror had focused on 11 separate days in July 2013 when Lord Hanningfield spent under 40 minutes on the Parliamentary estate after commuting from his home in Essex.
The Lords Privileges and Conduct Committee suspended Lord Hanningfield for the current Parliament after the revelations, saying he had "failed to act on his personal honour".
He was also told to repay £3,300 he had wrongly claimed.
The Metropolitan Police has confirmed that in light of Mr Kernaghan's report "a review of allegations of unlawful claiming of allowances at the House of Lords" had begun, adding that the investigation was "focused on Lord Hanningfield alone".
A force spokesman said: "We can confirm a 73-year-old man attended by appointment an east London police station and was interviewed under caution in relation to an allegation of fraud."
Peers are not paid a salary but can claim a maximum daily allowance of £300 if they attend a sitting or undertake "appropriate parliamentary work" in Westminster.
Lord Hanningfield, who was sentenced to nine months in jail in 2011 for fraudulently claiming parliamentary expenses, has said he regards the £300 allowance as a "de facto salary" which it is his right to claim.
He has said he will return to the Lords once his suspension is up.
Police are investigating a former Conservative peer suspended from the House of Lords over his expenses.