Jeremy Hunt has raised the plight of persecuted Christians around the world in an Easter message, after launching a trenchant defence of the Conservatives’ economic record following criticism from Jeremy Corbyn.

The foreign secretary, who is expected to be in the running to succeed Theresa May as Tory leader, has written 40 letters to Christian individuals and faith groups to mark the end of Lent.

In a series of tweets sent to the Labour leader, Hunt also defended David Cameron’s austerity programme. Rival Conservatives believe Hunt is attempting to raise his profile for a leadership campaign. Brexiters have dismissed him as “Theresa in trousers” while friends have claimed he has secured the support of as many as 75 MPs.

Up to eight cabinet ministers could yet launch a leadership bid, in a crowded field that Conservative MPs would have to whittle down to two. If Boris Johnson, the bookies’ favourite, makes that final pairing, it is expected he would be difficult to stop when the choice is made in a ballot of the party’s 120,000 members.

Hunt said in his Easter message he was appalled that 245 million Christians around the world faced persecution as a result of their faith. The Foreign Office said 300 Christians a month were killed because of their beliefs.

Hunt’s first letter was to 90-year-old Andrew van der Bijl, a Dutchman who smuggled copies of the Bible into the communist eastern bloc during the cold war and who founded the Open Doors charity.

The Foreign Office has acknowledged that the UK has not always reflected the suffering of persecuted Christians in its policy. Hunt has launched a review of the issue, led by the Rt Rev Philip Mounstephen, the bishop of Truro, who is due to report this summer.

Henrietta Blyth, the chief executive of Open Doors, said: “I welcome the foreign secretary’s independent review into the extent of UK government support for Christians facing persecution for their faith. This review is a great first step, but the proof of the pudding will be if it delivers concrete change for persecuted Christians and if its recommendations are also adopted by other government departments.”

Hunt, who voted for remain in the EU referendum, gave an interview to the New Statesman magazine in which he praised the “genius” of Cameron for persuading voters to accept cuts in public spending and called on the Conservatives to show they were the party of “prosperity with purpose”.

Corbyn retweeted a report of Hunt’s interview on Friday, adding the comment: “Austerity isn’t a political game. It has serious consequences.”

Hunt responded by writing that a Corbyn government could devastate the UK economy and destroy gains made under the austerity programme.

“Before you attack me for ‘austerity’, which put the economy back on its feet, perhaps ask why a Labour MP needs a bodyguard at a Labour conference and your party is under formal investigation for institutional antisemitism?” he wrote.