Labour leader Sir Keir Starmer said the Prime Minister has not “earned the right” of a knighthood once he leaves office.

Sir Keir’s comments about Boris Johnson come after the opposition leader dismissed criticism of Sir Tony Blair’s knighthood, insisting the former prime minister deserves the honour.

More than half a million people have signed a petition calling for Sir Tony’s appointment by the Queen to the Order of the Garter – the oldest and most senior British Order of Chivalry – to be rescinded over his domestic record and the Iraq War.

But Sir Keir insisted the honour is not a “thorny” issue and that Sir Tony had been a “very successful prime minister”.

After giving a speech in Birmingham about Labour’s priorities for 2022, Sir Keir was asked about the former prime minister’s knighthood, and whether Mr Johnson should be honoured in future.

He replied: “No, I am sorry, I don’t think that this Prime Minister has earned the right to have an honour.

“I do think Tony Blair has.”

In his speech, Sir Keir also paid tribute to the past Labour governments of Attlee, Wilson and Blair, adding they “made Britain a better country”.

He said: “We must be the people who write the fourth chapter. The people who create a new Britain in the 21st century.”

Sir Tony’s knighthood could clear the way for his successors in No 10 to be given similar honours, following reports that the delay in granting the accolade was blocking the others.

A Change.Org online petition calling for Sir Tony to be stripped of the honour had been signed by more than 544,000 people by Tuesday morning.

Sir Keir had earlier told ITV’s Good Morning Britain: “I don’t think it’s thorny at all; I think he deserves the honour. Obviously I respect the fact that people have different views.

“I understand there are strong views on the Iraq War. There were back at the time and there still are, but that does not detract from the fact that Tony Blair was a very successful prime minister of this country and made a huge difference to the lives of millions of people in this country.”

The Prime Minister’s official spokesman said: “Appointments to the Order of the Garter are a matter for Her Majesty the Queen, there is no involvement of the Prime Minister or Government, so it wouldn’t be one for me to comment on.

“I would point out every former prime minister before Tony Blair has received the Order of the Garter or Thistle.”

Asked whether Mr Johnson believed the signatories of the petition were wrong, the spokesman said it was “a matter for the Queen”.

It would also be a matter “entirely for Her Majesty the Queen” whether Mr Johnson receives a knighthood after leaving office, the spokesman added.

Meanwhile, vaccines minister Maggie Throup told LBC: “I think he [Sir Tony] did lots of good things. And I think it’s only right that we do honour our previous prime ministers. And he was prime minister for such a long time.”

In a hint that Gordon Brown, David Cameron and Theresa May could be in line for honours, she said: “I think obviously it now opens the doors for others to be recognised in the same way.”

Commons Speaker Sir Lindsay Hoyle has suggested that all former prime ministers should be offered a knighthood because “it is one of the toughest jobs in the world”.