Ahead of a crucial vote in the Commons on the measures on Tuesday, the Labour leader said his party would act in the “national interest”, but held back from committing to support the prime minister amid concern over economic support for areas in the north.
Sir Keir also said he was due to receive a briefing on Monday from England’s chief medical officer professor Chris Whitty and Sir Patrick Vallance, the chief scientific officer, and hear their expert opinion on the tiered system.
It comes as Mr Johnson faces intense opposition within Conservative ranks over his proposals to place the vast majority of the population under either Tier 2 or Tier 3 restrictions when England’s national lockdown ends on 2 December.
Reports have suggested dozens of Tory MPs may rebel and vote against the new measures, potentially forcing the prime minister to rely on Labour votes to get the contentious restrictions through the House of Commons.
Ed Davey, the Liberal Democrat leader, also said on Monday his party’s 11 MPs would withhold support for the government’s “unsafe plan”, describing the new tiered system as “arbitrary, confused and chaotic”.
Pressed on how he would direct his MPs to vote on the government’s proposals, Sir Keir said: “We’re having extensive discussions today with businesses, with communities, but equally important with the government’s scientific experts.
“Chris Whitty and Patrick Vallance and I have got a session this afternoon. I’ve been talking to them in confidence throughout the process and they have been really clear and open with me in confidence. I need to talk through with them what they think about this tiered system.
“Amongst my concerns is that we were in a tiered system before we went into lockdown and therefore if this tiered system isn’t better than the last one, we’re going to round and round in circles and I’m really worried about that.”
Answering questions from members of the public in his weekly “Call Keir” event, he went on: “I do think there are going to have to be restrictions, so we are not in the same place as some of those Conservative MPs who just say well you don’t need restrictions.
“We do need restrictions and I’m very conscious of the fact that however much I criticise the government’s approach… the Labour Party has to act in the national interest here.
“The national interest is how do we keep the virus under control, stopping the infection rate spreading because we all know what happens if it gets out of control. We’ll be balancing that but in the end the decision we make will be what’s in the national interest.”
Speaking on Sunday, the shadow foreign secretary Lisa Nandy also warned her party’s support for the government’s proposals was “not unconditional” while acknowledging Labour had “never voted against health restrictions”.
According to Labour analysis, areas in the North West placed under Tier 3 could miss out on millions from a government business support grant if ministers fail to extend the £20-per-head Additional Restrictions Grant (ARG) for regions going back into the most severe level of restrictions after the national lockdown.
Figures released by the party claimed Manchester’s weekly value of support could fall by £678,000 while Stockport and Wigan could both experience a fall of over £350,000. “The Conservatives are once again abandoning the North,” the Labour leader added as he urged the government to extend the economic support.
Sir Keir, however, is facing calls from within his own party to vote down the government’s proposals on Tuesday. Earlier, the former shadow cabinet minister Richard Burgon said he would not vote for the government’s new restrictions, posting in a statement the measures “repeat the errors of the past” and called for an extension of the lockdown until the Christmas period.
He warned: “The new tier system will not only fail to drive the virus levels down, but there’s a real risk that taking the foot off the brake over the coming weeks will undermine the gains made by the current lockdown. That will make a third wave and yet another lockdown much more likely in the new year.”
In an attempt to dissuade potential rebels from voting down government proposals, Mr Johnson wrote to Tory MPs at the weekend offering to end the system in February, after just nine weeks, and to give MPs a separate vote on whether or not the restrictions should continue until March.
In a letter, Mr Johnson added that with a vaccine in sight “now more than ever is the time to demonstrate unity and resolve”.