Michael Gove has been placed under investigation by Parliament's standards watchdog.
The investigation relates to his register of financial interests.
The details will not be published until the inquiry is concluded, and those under investigation are banned from discussing the allegations.
The investigation was opened on Wednesday.
Michael Gove has been placed under investigation by Parliament's standards watchdog
PA
Last week, it was reported that the Housing Secretary had failed to register VIP hospitality he enjoyed at a football match with a Conservative donor whose firm he had recommended for personal protective equipment (PPE) contracts during the coronavirus pandemic.
He attended a Queens Park Rangers match in 2021 with David Meller.
Meller Designs was handed six PPE contracts amounting to a value of £164 million following Gove's referral, the Guardian reported.
A spokesperson for the Housing Secretary said his failure to declare the two free tickets was an "oversight", adding that he has written to parliamentary authorities to alert them to the possible omission.
MPs are required by the code of conduct to register any gifts or hospitality worth more than £300.
Six MPs are currently under investigation by the Standards Commissioner, including Deputy Speaker Dame Eleanor Laing, Sir Bernard Jenkin and Virginia Crosbie.
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Prominent Tory backbencher Miriam Cates is also facing an investigation by the Standards Commissioner.
She is under investigation for “actions causing significant damage to the reputation of the house as a whole, or of its members generally”.