No 10 has admitted a funding boost may not be enough to cover the cost to hospices of its National Insurance raid on employers.

Ministers were accused of "giving with one hand and taking with the other" for announcing a £100 million funding boost for end-of-life care after raising employers' National Insurance contributions (NICs).

The Government described the £100 million funding as the biggest investment in the sector this generation, and confirmed £26 million in continued grant funding will continue next year, under what was known as the children's hospice grant.

Downing Street would not say if the funding boost would offset the increase in NICs that hospices face following Rachel Reeves' Budget, but acknowledged the money would ease pressures on the sector.

Asked whether the extra money would more than compensate for NICs increases, the Prime Minister's official spokesman said he would not "draw a kind of parallel".

The Conservatives said Labour was taking millions of pounds from hospices and palliative care charities with its NICs changes - and then telling them to be "grateful" to get some money back.

Neil O'Brien, the former Tory health minister, suggested the Chancellor was the "Grinch who stole Christmas" as he called on Thursday for charities and voluntary groups to be exempted from the NICs increase.

Hospice organisations have previously said their members would face further financial burdens without an exemption.

While Hospice UK said the latest funding, which is for England only, would be "hugely welcomed", Marie Curie, the end-of-life charity, warned a one-off investment would not be enough to make the improvements needed.

Dr Caroline Johnson, the shadow health minister, criticised Labour's "audacity" for "taking millions of pounds off hospices and palliative care charities and then [thinking] they should be grateful when they give them some of it back".

She added: "This is socialism at its finest."

Sir Bernard Jenkin, the Tory MP, said a hospice in his Harwich and North Essex constituency estimated the NICs changes will cost them £300,000 a year, asking: "Can the minister now give a guarantee that they will be compensated by the Government in full?"

Karin Smyth, the health minister who unveiled the funding, replied: "We will announce allocations for the whole sector and the NHS in the usual way in the new year."

Martin Vickers, the Tory MP, said any increase in funding was welcome, but added: "This, let's be honest, is giving with one hand and taking with the other."

Wes Streeting, the Health Secretary, said in a written statement it was "only right" hospices were given financial support, while Stephen Kinnock, the care minister, said the funding would "allow hospices to improve their physical and operational environment, enabling them to provide the best possible care to their patients".

Toby Porter, the Hospice UK chief executive, said: "Today's announcement will be hugely welcomed by hospices, and those who rely on their services. Hospices not only provide vital care for patients and families, but also relieve pressure on the NHS.

"This funding will allow hospices to continue to reach hundreds of thousands of people every year with high-quality, compassionate care."

Ralph Coulbeck, chief executive at Haven House children's hospice, said it was "a relief" to know the children's grant was being maintained next year, adding that it would "help to support the vital care we provide to seriously ill children and families".

Matthew Reed, the Marie Curie chief executive, described the palliative and end-of-life care system as being "in crisis" with access to the right care depending often on where someone lives.

He welcomed the additional investment but warned: "A restricted and one-off investment is not going to meet the recurring cost pressures, and ongoing needs of the sector - including the long-term implications of additional NICs, ongoing pressures as a result of rising costs of pay, and increased numbers of people dying over the next 20 years."

Mr Reed said "radical change" was needed and called for a palliative care strategy supported by a sustainable funding framework.