PRIME Minister Boris Johnson will lead a press conference at Downing Street this afternoon, No 10 has said.

He will be joined at the 5pm briefing by chief medical officer Professor Chris Whitty and MHRA chief executive Dr June Raine.

The press conference has likely been organised in response to concerns over the UK's vaccine supply, with leaked letters from the NHS warning of a slow down in the arrival of supplies.

Here are three things the Prime Minister could talk about tonight:

Vaccine delays

A leaked NHS letter shows health chiefs are bracing themselves for a significant drop in doses by March 29.

First doses of the jab are expected to be 'constrained' for around four-weeks.

It has inevitably led to fears about an extension of lockdown, and when people will now be given the vaccine.

Earlier today Health Secretary Matt Hancock said that a batch of 1.7 million Covid-19 vaccine doses have been delayed.

He told the Commons: “In April, supply is tighter than this month and we have a huge number of second doses to deliver. During April, around 12 million people, including many colleagues in this House will receive their second dose.

“These second doses cannot be delayed as they have to be delivered within 12 weeks of the first dose.

“In the last week, we’ve had a batch of 1.7 million doses delayed because of the need to retest its stability.

“Events like this are to be expected in a manufacturing endeavour of this complexity and this shows the rigour of our safety checks.”

You can expect the Prime Minister to pick this up at the briefing.

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Lockdown update

Lockdown restrictions are set to be eased further at the end of the month.

However, the Government has said restrictions can only be relaxed if certain tests are met.

These include the number of people vaccinated in Britain an so Mr Johnson will likely address whether the delay to supplies could have an impact of lockdown easing.

Covid rates

One of the other tests which must be met before lockdown rules are eased is Covid rates must be moving in the right direction.

Mr Johnson will, along with Prof Whitty, likely provide an update on the latest rates and the number of deaths in the UK.

Health Secretary Matt Hancock said at a briefing on Wednesday the vaccination programme was bringing down the number of Covid deaths sharply.