The independent fiscal watchdog will deliver a forecast to the Chancellor next week as the Government scrambles to curb the chaos in the markets following the mini-Budget.
The Prime Minister and Chancellor Kwasi Kwarteng held crunch talks with experts from the Office for Budget Responsibility (OBR) this morning which lasted less than 48 minutes.
Richard Hughes, Andy King and Professor David Miles, members of the OBR's budget responsibility committee, were seen walking into No11 at 9.45am. They emerged into Downing Street again at 10.33am.
In a statement after the meeting, the watchdog said it would provide a forecast to the Chancellor on October 7 based on "our independent judgement about economic and fiscal prospects and the impact of the Government’s policies."
But the Treasury said the details wouldn't be published until November 23, when Mr Kwarteng delivers his next financial statement.
Ms Truss has been under intense pressure to U-turn on her tax-cutting mini-Budget after the pound crashed to a record low against the dollar and the cost of Government borrowing soared.
The Treasury rejected calls to bring the forecasts forward and said they will be published on November 23, when Mr Kwarteng is due to set out a "Medium-Term Fiscal Plan".
A spokesperson said they had agreed to "work closely" with the OBR and the Prime Minister and Chancellor "reaffirmed their commitment to the independent OBR and made clear that they value its scrutiny".
Treasury and Downing Street sources claimed earlier that it wasn't an emergency meeting - despite the fact it is unusual for the PM to sit on talks with OBR chiefs.
Treasury Committee chairman Mel Stride said the meeting must be a "reset moment" amid growing Tory jitters over the fallout from Ms Truss's economic plans.
Mr Kwarteng has faced calls to bring forward his planned statement setting out how he intends to get the public finances back on track after the OBR said it could produce a preliminary set of forecasts by October 7.
Critics are likely to seize on this six-week gap and demand to know why the OBR's initial forecasts aren't being published sooner.
Labour warned the PM and the Chancellor had lost the confidence of the markets and the public.
Asked whether Liz Truss's meeting with the Office for Budget Responsibility will reassure markets, shadow business secretary Jonathan Reynolds told Sky News: "It's a bit late for that now, isn't it?"
He added: "I cannot stress how angry people should be at this Government for what is without question one of the biggest unforced errors in policy-making in this country's history."
Mr Reynolds claimed that people and businesses are looking at the "entire approach" of the Government and "saying we have no faith in these institutions".
"I will be frank," he said. "I don't think either the Prime Minister or the Chancellor will ever get that back."
Liberal Democrat Leader Ed Davey said: “Delaying this forecast means shutting the door long after the horse has bolted.
“Liz Truss and Kwasi Kwarteng are allowing the economy to fly blind for two months, while their reckless plans cause pension and mortgage misery for millions of British people.
“Families and businesses can’t afford to wait any longer for this government to fix their botched, unfair Budget. Truss and Kwarteng must cancel the Conservative Conference, recall Parliament and propose a new Budget now, before any more people lose their homes or close their business.”
