Brandon Lewis has said Boris Johnson has his “100%” loyalty, despite the prime minister being sent questions by police investigating alleged lockdown breaking parties.
The Northern Ireland secretary said he had “absolute confidence” in Johnson.
Speaking to the BBC’s Sunday Morning programme, Lewis would not be drawn on whether he would still back the PM should he be fined for breaching Covid rules.
But he said: “I give 100% loyalty to the prime minister. I think this is a prime minister who will go on and fight successfully the next election.
“He has my full support. My loyalty goes to the prime minister and the people of the United Kingdom.”
More than 50 people who are believed to have attended parties in Downing Street and Whitehall are being contacted. On Friday No.10 confirmed Johnson was one of them.
The Metropolitan Police said it would be sending notices asking for “an account and explanation of the recipient’s participation in an event”.
Officers working on so-called Operation Hillman are investigating 12 events.
The prime minister is alleged to have been at up to six of them, including the “bring your own booze” party in the No 10 garden in May 2020 during the first lockdown.
Johnson has refused to say whether he would resign should he be issued with a fixed penalty notice by police.
Fifteen Tory MPs have publicly called for Johnson to quit, while more are thought to have privately written to the 1922 Committee of backbench Tories calling for a no-confidence vote.
More are poised to do so if the prime minister is found to have broken his own coronavirus laws, or further damaging details emerge from the Sue Gray inquiry.
He will face a vote of no confidence if 54 Conservative MPs write to 1922 Committee chairman Graham Brady, and would be ousted if more than half of his MPs subsequently voted against him.