Labour has accused Boris Johnson of misleading voters over a promised £1.8 billion cash injection.
Boris Johnson's announced twenty hospitals will benefit from the cash boost but he has been accused of "sweeting up" the public before a possible general election.
Speaking during a visit to the Pilgrim Hospital in Boston, Lincolnshire - one of the hospitals set to benefit from the increase - Mr Johnson was adamant that the £1.8 billion was new money.
"It's part of a national programme that the NHS asked for and I want to stress this is new money," he said.
"I said 10 days ago on the steps of Downing Street, that we would be upgrading 20 hospitals - 20 new hospital upgrades around the country - and this is it."
Reacting to the news Dr Mark Pickering, chief executive of the Christian Medical Fellowship told Premier's News Hour it's natural to be sceptical.
He said: "I think any money for the health service is excellent news but the health service is a massive operation and even sums of billions of pounds don't make a lot of difference.
"There's always questions about where that's actually coming from and I guess the bottom line is the NHS is an immensely complex organisation and we have to have realistic expectations about how much you can achieve by throwing money at it."
Encouraging Christians to pray for the NHS, he said: "I think what's most important for us is that we pray for those in authority, both the Prime Minister, the health secretary, and particularly those who are managing and commissioning health services across the country.
"We tend to focus just on the doctors and nurses - they're of course, incredibly important to the health service - but we need to pray for people who are making day to day decisions about where we spend this money and how we make it more effective and then those making decisions about staffing and workforce planning."
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