A Government offer of a £2.5 billion financial package to support the return of the Stormont executive is a “short-term sugar rush”, Alliance Party deputy leader Stephen Farry has said.

Representatives from the five main Stormont parties will return to Hillsborough Castle on Tuesday for technical talks on the offer.

Northern Ireland Secretary Chris Heaton-Harris outlined the details to party leaders on Monday as part of an attempt to stabilise the region’s finances and encourage a return of the powesharing institutions.

But the party leaders have said the package, which includes a lump sum to settle public sector pay claims, does not contain enough money.

Sinn Fein has said Wednesday should be a cut-off point for talks with the Government, while the DUP has insisted there is some way to go both in talks on public finances and on discussions to reach a deal on post-Brexit trade arrangements.

Mr Farry said more work needs to be done on the proposed financial package.

“It is in the right space, talking about some of the right ideas in terms of things that need to happen but the quantums of money on the table are simply not sufficient,” he told the BBC Good Morning Ulster programme.

“This is about the future of Northern Ireland and we need to make sure that Northern Ireland has sufficient resources to have sustainable public finances.

“As things stand this is not the case. The figures offered yesterday aren’t deeply embedded into our finances.

“We will get a short-term sugar rush in terms of resources, but we will be back in the same situation within 18 months to two years and that doesn’t really serve anyone’s interests.”

Ulster Unionist MLA Steve Aiken said his party had submitted a list of questions about the offer.

He added: “There is a substantial amount of money up front when you initially look at it.

“We should, if we agree to it and we get the Assembly and executive back up and running, be able to cover public sector pay.

“But then we have to look at how we are going to manage finances going forward.

“There is a lot of the detail we need to tease out today.”

SDLP MLA Matthew O’Toole said: “It is clear that often when large numbers are announced there is devil in the detail and that is the case this time.

“But it is also clear that the parties which are going to form an executive now have the opportunity to collectively work to get a package that they believe they can deliver on.

“Then they should be held accountable for their ability to deliver on that.”

The proposed measures in the Government offer include funding for public sector pay rises this year, reform of the funding model for Northern Ireland, including the setting of a new fiscal floor and increasing the period by which Stormont has to pay back a budget overspend.

Devolved government has not been functioning in Northern Ireland for nearly two years because of the DUP’s ongoing boycott of the institutions in protest at post-Brexit trade agreements.

The DUP has been in negotiations with the Government to secure legislative assurances over Northern Ireland’s economic position in the UK.