John Healey will face questions from MPs on Thursday amid reports of Storm Shadow missiles provided by Britain being used by Ukraine within Russia.
The Defence Secretary is due to appear before a parliamentary committee in which he is likely to be grilled on the UK’s position on support for Kyiv.
Storm Shadow’s use in Russia comes a day after Moscow said American long-range weapons had been fired into its territory.
Wreckage from one of the long-range weapons has been found in Russia’s Kursk region, which borders Ukraine, with up to 12 of the missiles deployed, according to multiple reports.
Meanwhile, Russian President Vladimir Putin has lowered the threshold for using nuclear weapons, after US President Joe Biden gave Kyiv permission to fire US ATACMS long-range missiles into Russia.
Downing Street would not comment on the reports.
Mr Healey was due to appear before the Commons Defence Committee at 10.30am – while the House of Lords was expected to hold a debate on Ukraine led by Lord Peter Ricketts, chairman of the European Affairs Committee, later in the day.