The Sunday Telegraph and Sunday Times newspapers quoted Conservative finance minister Sajid Javid as calling Labour’s spending plans “truly frightening” that would push Britain close to bankruptcy.

However, Labour’s would-be finance minister, John McDonnell, dismissed the Conservative estimates as “ludicrous” and a “mish-mash of debunked estimates and bad maths”.

Labour has not yet published full policy proposals, and the Sunday Times said the Conservative Party based the 1.2 trillion pound figure on Labour’s manifesto for the 2017 election and more recent policy pledges.

Britain’s top civil servant barred the finance ministry from publishing a costing of Labour’s policies last week, saying it would breach political impartiality rules.

McDonnell said in an interview for the Sunday’s Independent that the party’s manifesto would be “the most radical ever” and include a pilot for a universal basic income, and reiterated his desire to block expansion of London’s Heathrow airport.

The Conservatives currently enjoy a sizeable lead in opinion polls over Labour at the start of the campaigning for December’s election, which Johnson called early in a bid to break the parliamentary impasse over Brexit.

Separate polls for the Mail on Sunday and Observer newspapers both put the Conservatives on 41% and Labour on 29%, while a Sunday Times poll put the Conservatives on 39% and Labour on 26%.

Both Javid and McDonnell unveiled significant spending plans last week.