FILE PHOTO: Britain's former foreign secretary Boris Johnson walks to Downing Street in London, June 26, 2018. REUTERS/Toby Melville/File Photo

LONDON (Reuters) - Boris Johnson, Britain’s former foreign secretary, on Sunday called on the government to use its international aid budget to focus on national priorities amid speculation about whether he will challenge Prime Minister Theresa May.

Johnson, who left the government during the summer over his opposition to May’s Brexit plans and is the bookmakers’ favorite to replace her, has declined to say whether he would challenge her for the leadership.

In his latest newspaper column, Johnson did not mention Brexit and instead said Britain’s aid budget should be shifted to projects “consistent with the political and commercial priorities of this country.”

“Everywhere you go, you will find other countries that subtly or openly use their development aid budgets as leverage to support their exports, or other popular objectives,” Johnson said.

“It was infuriating to travel to South East Asia, and see for instance how Japanese contractors were supported by development assistance, as they applied for contracts, in ways we deem to be illegal.”

Britain has an aid budget at 0.7 percent of economic output and the target has previously come under fire from lawmakers who say it is a blunt tool that is too high and should be spent in Britain itself.

“If we are going to spend so much on aid – and there is no doubt that it wins Britain friends and admirers around the world – then let’s get value for this country as well,” Johnson said.