London - British Chancellor of the Exchequer Philip Hammond says he is committed to Britain's plan to leave the EU single market and customs union after Brexit.

The comments come amid rumours of growing rifts in Prime Minister Theresa May's Conservative party. Hammond was pressed in parliament by a Conservative lawmaker to say whether he was "absolutely, personally and enthusiastically committed" to May's Brexit plan.

"Yes, I've made it clear on many occasions that when we leave the European Union on March 29, 2019, we will also leave the single market and the customs union," he said, following a cabinet meeting with May and other ministers earlier Tuesday. "Those are matters of legal necessity," Hammond said.

Officials quoted by the BBC and other media said May had called for "strength and unity" from her cabinet, stressing the need for confidentiality after apparent leaks in recent days.

Continuing the  partnership

Hammond said his priority for Brexit was to agree the "closest and deepest possible partnership with our European neighbours that allows us to continue patterns of trade and business, patterns of security cooperation ... as we enjoy now."

In recent speeches, Hammond appeared to advocate a softer Brexit than envisaged by May and other ministers, supporting the agreement of a transitional period to "avoid unnecessary disruption and dangerous cliff edges" when Britain's two-year Brexit negotiating period ends in early 2019.

Speculation has mounted since the Conservatives' disappointing performance in a snap election on June 8, when May lost her parliamentary majority, that she could soon face a leadership challenge.

Former Conservative minister Michael Heseltine, now a member of parliament's unelected upper house, the Lords, told Sky News he expected the divisions to continue to cause friction in the party.

Hard Brexit, soft Brexit

"My anxiety is that it has been going on for so long - it's so deeply ingrained in the bitterness of the Brexit debate - that it's very difficult to see how it can be stopped while Brexit is the serious agenda of the Conservative party," Heseltine told the broadcaster. "They've gone on and on, and they've now got to the point where they have divided the Conservative party," he said.

Speaking to the Irish Examiner on Monday, Michael Creed, Ireland's agriculture minister, said there appeared to be "no political coherence" in the British government and "no leadership on Brexit."

"Various ministers talk about hard Brexit, soft Brexit, no deal being better than a bad deal," Creed told the newspaper, adding that the "lack of any coherence is a huge problem" for Ireland.