Arlene Foster has told the Secretary of State that Westminster should not "interfere" with Northern Ireland's abortion law and it should be up to MLAs to make decisions on the issue.
he DUP leader met Brandon Lewis at Stormont on Friday to discuss a range of issues, including Brexit.
The Secretary of State also met the Ulster Unionists.
Afterwards Mrs Foster released details of a letter on abortion that she had given him.
She said that since devolution had been restored, it was up to MLAs to decide abortion law.
"The fact that the Northern Ireland Assembly was not functioning last year was used to justify the highly unusual occurrence of Parliament legislating on a sensitive devolved matter," she said.
"HM Government has consistently maintained that it would not interfere with the Northern Ireland legal position, and that it was for a Northern Ireland Executive and locally elected public representatives to determine."
Mrs Foster said that "the DUP along with other parties believe the Assembly chamber is the appropriate place to deal with abortion".
"It should be elected representatives from Northern Ireland, representing the electorate who voted for them, taking the decisions," she added.
Under Section 9 of the Northern Ireland (Executive Formation etc) Act 2019 passed last July, the government must introduce new abortion laws to come into effect here on March 31.
Mrs Foster described her meeting with Mr Lewis as "useful and constructive". She voiced her opposition to an Irish Sea border and said Britain was Northern Ireland's "largest market and it is critical that we have unfettered trade with that market".
UUP leader Steve Aiken said he had a "very frank discussion" with the Secretary of State.
He told him that the Government must act on the issue of air passenger duty following Flybe's collapse.
Calling for more NHS funding, Mr Aiken said: "Before the first cases of coronavirus were diagnosed in Northern Ireland, Health Minister Robin Swann stated publicly that the health service needed £661m to address waiting lists and maintain the service.
"It is now more vital than ever that the health service gets the investment it needs and the Government has a major role in seeing that delivered."
Mr Aiken repeated UUP objections to the legacy proposals in New Decade, New Approach.
"The last thing Northern Ireland needs is the 'Ulsterisation' of legacy where former police and soldiers here are left high and dry whilst those in Great Britain are allowed to move on.
"That would be totally unacceptable. The Secretary of State was left in no doubt about our views," he said.
Meanwhile, both Mr Aiken and Mrs Foster stressed that their parties would not engage in political conversations about a united Ireland. They were responding to remarks by Alliance leader Naomi Long that she would be willing to be involved in discussions about Northern Ireland's constitutional future and urging unionists to do likewise.
"I can assure you that nobody from the Ulster Unionist Party is going to be involved in any conversation about a united Ireland - not now, not ever," said Mr Aiken. Asked if Mike Nesbitt would take a different view, he added: "I, as the leader of the Ulster Unionist Party, make it very clear.
"Shall I say it again? The Ulster Unionist Party will not be involved in any conversation about a united Ireland. Not now, not ever."
Mrs Foster said: "Time spent talking about a united Ireland is not time spent dealing with the things that we need to deal with which is around health, which is around education, the things that matter most to people."