The Labour leader lashed Prime Minister Boris Johnson’s Government for being “too slow to act” throughout the Covid-19 pandemic.
Writing in The Guardian, the MP for Holborn and St Pancras warned the nation is at a “crucial point” in the fight against the virus.
He said that Britain faced “a long and bleak winter” if immediate steps were not taken to ensure the country was better prepared for a second wave.
In particular, Sir Keir pointed to the Government’s lack of clear communication throughout the crisis and its Test and Trace programme as the areas most in need of rapid improvement.
He wrote: “On the occasions that the government has acted at pace, it has too often done so without a clear plan. Trying to get answers and clarity from the prime minister is a frustrating experience.
“His repeated refusal to accept that test and trace isn’t functioning properly is a roadblock to fixing the issues and restoring public confidence.”
The NHS Test and Trace programme has recently come under fire for not reaching enough people who have tested positive or their close contacts, with researchers warning that the system in its current state would not be enough to stave off a second wave in the winter.
Sir Keir also stressed that reopening schools for the new term must be a priority and further steps needed to be taken to ensure the NHS was ready to cope with another potential spike in infections.
“Any steps the government makes to regain the trust of the British people will have Labour’s full support,” he wrote.
“But the reality is that if the government doesn’t use this summer wisely, focusing on driving down the rate of infection, Britain faces a long and bleak winter.”