Patients needing urgent cancer and other tests will now have to wait until March 2025 before six week targets are met.
Maximum six week waits for diagnostic tests were introduced by Labour in 2008 with a pledge that no more than one in 100 patients would have to wait longer.
But when the pandemic reached its height in 2020 58% of patients were not getting vital scans within six weeks.
The PM has opened 90 community diagnostic centres since last year with plans for 70 more to speed up the process.
Mr Johnson said: “The pandemic put unparalleled pressure on our NHS, but we are making excellent progress towards our goal of tackling the Covid backlogs.”
And Health Secretary Sajid Javid added: “There is no quick fix, but between community diagnostic centres, new cancer screening, and expanding mental health provision, we are supporting the NHS to tackle the Covid backlog.”
Mr Javid will this week provide more information on the Innovative Medicines Fund to support patients with rare and genetic diseases.
The Department of Health and Social Care (DHSC) signalled ministers will be making series of announcements in the coming week on the progress that the £12 billion-a-year catch-up programme is making.
The Government is also expected to publish a review into health and care leadership by General Sir Gordon Messenger, a former vice-chief of the defence staff, aimed at ensuring the cash injection is spent efficiently.
But with some Westminster observers predicting he could face a confidence vote by Tory MPs as early as this week, the Prime Minister may struggle to shift the news agenda.
A steady stream of Conservatives has being coming forward to call on Mr Johnson to quit since Sue Gray’s report into lockdown violations in No 10 and Whitehall was published at the end of last month.
Under party rules, he will face a confidence vote in a secret ballot if 54 Tory MPs submit a letter to the chairman of the backbench 1922 Committee, Sir Graham Brady, calling for one.