Health Minister David Clark has rejected claims he and other Government Ministers have been "gagged" - as he fronted today to announce a $160 million boost to Pharmac health spending.

An email from the Prime Minister's office, obtained by the Herald, directed ministers' press secretaries to issue only "brief written statements" in response to all media queries following a huge release of official documents related to Covid 19 on Friday.

"Do not put Minister up for any interviews on this," the email said.

"There's no real need to defend because the public have confidence in what has been achieved and what the Govt is doing. Instead we can dismiss."

Clark rejected an assertion he had been gagged. "Obviously I am here."

He said he had not personally received the memo, but saw it after it became a story. He did not believe the Government was arrogant.

"I am here, happy to answer questions that journalists might have. This is the advice we have received. We have looked at that advice and then made decisions."

Clark was in front of reporters to annouince the Government will bolster Pharmac's budget by an extra $160 million to ensure that it, and New Zealand's District Health Boards, have access to more medicines and vaccines.

While there has been little specifics on where the extra money will be spent, Health Minister David Clark said today if a Covid-19 vaccine became available, the Government would ensure Pharmac had the money to get hold of it. A vaccine was still likely to be 12 months away.

The new funding is split across the next four years, with $10 million being paid out next financial year, and the remaining $150 million over the other three.

Today's pre-Budget announcement comes just four days before Thursday's "recovery Budget" – it's one of the few new funding announcements that have been signalled before Budget Day.

Clark said that these are not "normal times" and Thursday's Budget would have a "significant" focus on recovery and rebuilding.

But Clark told reporters that securing medicine supply was also "critical" for ensuring the wellbeing of New Zealanders. He said this was more vital now than ever.

He said the extra money for Pharmac was important, given the global pressure on supply chains.

"This [funding] will secure our medicine supply, while at the same time allowing scope for Pharmac to continue to work on expanding the range of funded treatments where possible."

As the world has been grappling with the Covid-19 pandemic, the global medicine market has been tight – meaning it's been harder and more expensive to buy medicines.

Pharmac is the New Zealand Government agency that decides which medicines and medical devices are funded in New Zealand.

It gets its funding from the Government, but Ministers are not allowed to directly tell the agency what to buy.

Pharmac chief executive Sarah Fitt welcomed the news, but said the fiscal impacts of Covid-19 were not yet known.

She said Covid-19 was making it harder for Pharmac to buy medicines - the new funding would help make it easier to the agency to precure medicines.

Fitt said critical care medicines were now one of the hardest to come by. Pharmac has been building up its stock.

She said the cost of getting medicines to New Zealand had increased dramatically.

This is because getting freight into the country has been reduced dramatically, as the world battles with Covid-19.

Fitt said there were a number of medicines that Pharmac was looking to buy, which had been put on hold.

Clark said it was vital that the Government prioritises additional investment in critical services like Pharmac, as it grappled with the health and economic impacts of Covid-19.

Since last year's budget, Pharmac has approved 13 new medicines, to be publicly funded – this includes six new cancer treatments.

Today's announcement is on top of a $60 million boost to Pharmac in September last year, and a recent $35 million one-off top-up in funding to help respond to Covid-19.

The new funding means Pharmac medicine budget is $1.045 billion.

"This Government is committed to improving the health and wellbeing of all New Zealanders. Protecting our medicines supply by continuing to invest in Pharmac does just that," Clark said.