Chancellor Rachel Reeves has refused to rule out tax hikes as she confirmed government support for an expansion of Heathrow Airport.
In a speech on Wednesday, Reeves backed plans for a third runway at the UK’s busiest airport, arguing it was "badly needed".
The case for the additional runway was "stronger than ever," Reeves said, adding government planning reforms meant "delivery of this project [was] set up for success".
Reeves also failed to rule out another round of tax hikes in spring, saying plans would be made after the Office for Budget Responsibility’s latest forecast in March.
“I’ve been really clear about the fiscal rules. They are non-negotiable,” she said.
“They are what give stability to our economy but we’re still two months off and a lot of things happen in that time.”
Some £40 billion worth of tax hikes were unveiled in October’s Autumn Budget, including on employer national insurance, which has led businesses to warn over waning investment and higher prices ahead.
On Heathrow, she added: "We will take forward a full assessment through the airport National Policy Statement.
"This will ensure that the project is value for money, and our clear expectation is that any associated surface transport costs will be financed through private funding, and it will ensure that a third runway is delivered in line with our legal, environmental and climate objectives."
Having long planned the expansion, Heathrow has previously suggested the third runway would be scrapped without government support.
Reeves’ backing comes despite opposition within the Cabinet, alongside from backbenchers and Mayor of London Sadiq Khan.
Her speech, made at German firm Siemens' Oxfordshire factory, also detailed other projects aimed at boosting growth.
Alongside flagging the possibility of an Oxford to Cambridge "growth corridor", Reeves also floated the reopening of Doncaster Sheffield airport and the likes of a mass transport system for West Yorkshire.
IAG, which owns Heathrow's biggest operator British Airways, gained 2.6% on Wednesday.