Ms Truss is due to travel to Brussels next week to try to hammer out a deal on issues around the Northern Ireland Protocol which she says pose a threat to peace.
She wants to strike a deal before the Stormont election in May – in which Sinn Fein is expected to be the largest party – and is urging the European Union to show greater “pragmatism”.
Brexiteers are pushing Ms Truss to demand sweeping protocol changes and not just changes to customs control arrangements.
Sammy Wilson, one of the DUP’s most ardent eurosceptics, has urged Ms Truss, who is seen as one of the leading candidates to succeed Boris Johnson in any future leadership election, to follow the example of Lady Thatcher.
He said: “Ms Thatcher won the hearts of her party and the country by standing up to the EU defying its unreasonable budget demands in the 1980s. [Acting] as a true leader who spoke the language of the common people of the UK and was not constrained by the diplomatic doublespeak of the civil service establishment, she threatened to use her purse against hardline politicians of the EU and she succeeded.
“As she enters a period of intense negotiations with Maroš Šefčovič, Liz Truss should learn from the leader she seems to want to emulate.”
Mr Wilson has warned Ms Truss against striking a deal that does not address his main concerns over the protocol, which is accused of disrupting trade between Northern Ireland and Britain.
“If that is the extent of her negotiating objectives, she will not even have scratched the surface of the damage that the NI protocol is doing to the integrity of the UK, to the sovereignty of the UK parliament in its own country, to the undermining of NI’s constitutional position as part of the United Kingdom, the damage done to the peace process in NI and the institutions that underpin it, and the economic damage that is done to NI’s economy.
Northern Ireland and the jurisdiction of the European Court of Justice are completely removed, so it does not even have a say in the interpretation of the law. [The] the current arrangements undermine the constitutional integrity of the UK and furthermore they positively undermine the Belfast/Good Friday Agreement.
He said, “They need to know we’re serious and won’t be pushed around.”
Ms Truss said she was prepared to use Article 16 if an agreement could not be reached, but her ‘overwhelming preference’ is seen as a negotiated outcome.
A source close to the foreign minister said: “Basically the EU will have to be more flexible if we want to get a deal. Liz’s top priority is to uphold peace in Northern Ireland.
“The EU has a responsibility to help solve this problem because if we don’t, stability in Northern Ireland will be at risk. Northern Ireland is not part of the single market and the EU must stop treating it as such.
“We need more open-mindedness and creative thinking to get a deal done and that’s what we hope to see over the next few weeks.”
Last week Ms Truss and Mr Šefčovič met face to face for the first time since she took over responsibility for the UK’s negotiations with the EU following the resignation of Lord Frost last month . They met at his official country residence, Chevening House in Kent, and at a welcome dinner on Thursday evening they enjoyed Scottish smoked salmon, Welsh lamb, Kentish apple pie and Northern Irish whiskey.
Mr Wilson of the DUP said: ‘There’s nothing wrong with Liz Truss having a nice dinner with Maroš Šefčovič, but she should keep the purse under the table ready to go.’