DUP leader Arlene Foster has said that Sinn Fein are insisting on imposing the Irish language on everyone in Northern Ireland
Mrs Foster was speaking on BBC One's Andrew Marr Show on Sunday morning.
In a wide-ranging interview Mrs Foster discussed Brexit, her party's confidence and supply deal with the Conservative government and attempts to restore power-sharing at Stormont.
Mrs Foster rejected Sinn Fein President Mary Lou McDonald's recent use of the term "Londonderry" as a gesture to the unionist community.
The Fermanagh and South Tyrone MLA said the party should make a real gesture to unionists.
"I don't accept that they've made any so-called gestures and I think it's more important to find and build a basis for a shared community in Northern Ireland which is what we want to see, real sharing, and not just gesture sharing," Mrs Foster said.
"Wouldn't it be good if Sinn Fein were to allow Northern Ireland's government to sign up in full to the military covenant and to respect veterans regardless of where they live in the United Kingdom?"
The Armed Forces Covenant is a government promise that those who serve or have served, and their families, are treated fairly.
Mr Marr asked what the DUP could give Sinn Fein in return.
"I have said frequently that the Irish language is no threat to the United Kingdom or indeed to the union, I respect people that speak it, but that's not enough for Sinn Fein, they want to impose the Irish language on everyone in Northern Ireland.
"I think that would be not only a retrograde step, but for the Irish language as well because it politicises it."
Mr Marr asked Arlene Foster if she discussed issues surrounding Brexit like staying in the European Union (EU) customs union to prevent a hard border in Ireland with Prime Minister Theresa May.
"We have continuous conversations around this issue and I spoke to the Prime Minister yesterday afternoon," the DUP leader said.
"We want to see a sensible Brexit, by respecting the vote of the British people and leaving the customs union.
"We don't want what the EU have put on the table a red line down the Irish sea, what we seek to do is to protect the integrity of the United Kingdom from a constitutional and economic point of view."
Mr Marr asked if staying in the customs union would be a price worth paying for a soft border.
"The British people voted to leave the customs union, we don't believe we have to stay in it to have free flow between ourselves and the Republic of Ireland," Mrs Foster replied.
"Proposals have been put forward by the government and they have been dismissed out of hand by the EU.
"We would like to see less rhetoric and and more engagement.
"As Nigel Dodds said our fundamental red line is we have to move in step with the rest of the United Kingdom."
Mr Marr suggested the DUP would not bring down the government through their confidence and supply deal because they would not do anything to help Jeremy Corbyn become Prime Minister.
"We do think Jeremy Corbyn is beyond the pale due to his support for the IRA in the past, and as someone who's suffered as a result of IRA terrorism it is a very personal issue for me," Mrs Foster said.
"In terms of bringing down the government, we don't need to bring down the government because Theresa May was very clear about her unionist credentials long before she got involved with the DUP."
Sinn Fein MEP Martina Anderson said the DUP are continuing to ignore the views of the people of the North on Brexit.
"The fact is that the majority of people from the north, from all backgrounds, voted to remain in the EU," Mrs Anderson said.
"Arlene Foster may feel the need to repeat the Tory dogma on Brexit but in doing so she is going against the majority of people in the north.
"When I meet people from all sectors from across the north it is clear they want to remain in the EU and that is what we are about and it is also what Arlene Foster's boss, Theresa May, should be focused on.
"The British government need to come up with credible proposals in the current Brexit negotiations which would give effect to the views of the majority of people in the north."