Andrew Lansley has mounted a defiant defence of his unpopular NHS reforms, claiming that the changes will stop the service from collapsing.

In a strongly worded article in the British Journal of Nursing (BJN), the health secretary lambasts Labour's "hypocritical" opposition to his plans to extend competition in the NHS and shrugs off the sometimes vitriolic criticism he inspires.

"Some people say we should not have embarked on this programme of NHS reform. To those people who doubt what we are doing I would say, because of the pressures we are facing, we cannot afford not to reform the NHS. To take the approach advocated by Labour of simply sitting on our hands would be storing up a crisis for the future", Lansley writes.

Caring for the ageing population and covering the annual £600m of new drug treatments mean NHS costs are rising at an unaffordable rate and underline "why we need to rethink how the system works," he writes.

"Not reforming the NHS would have been a much easier decision for me as secretary of state to have taken. We could have just protected the NHS from cuts, put in an extra £12.5bn and left it there. But sooner or later the cracks would have started to show. New treatments would have been held back. Queues would have grown. Patients would have been let down," he adds.

The health secretary insists that criticism from the medical profession has not altered his determination to push through the biggest overhaul of the NHS since it was created in 1948.

"So frankly I don't care if I come out of this reform process under attack from the professions and the opposition. All I care about is that we avert that crisis and give the NHS the support it needs for the future.

"I didn't go into politics because I wanted to win a popularity contest. I decided to work in public service because I want to help improve my country for future generations and that is what we are working to do."

Lansley rejects the common criticism, which is even made privately by people close to him, that he has done a poor job of selling his plans to health professionals and the public. Instead he attacks the critics for distorting his plans. "People often argue that the reforms have not been communicated well, but the level of misrepresentation and wilful distortion of what is in the [health and social care] bill has led to many people being very confused about what we are trying to achieve," he writes.

His robust and defiant justification of the reforms has prompted fresh criticism from Labour that he is demonstrating a "siege mentality" and wrongly dismissing criticism.

Andy Burnham, the shadow health secretary, said: "The health secretary has demonstrated once again why we are in this problem; his dismissive attitude and inability to listen. His siege mentality is preventing him from seeing the bigger picture. The NHS has been repeatedly judged to be the most efficient healthcare system in the world, according to the independent Commonwealth Fund."

The article comes as peers in the House of Lords prepare to scrutinise the bill for the seventh and last day of its report stage. They will debate the regulation of healthcare assistants and social workers, the role of the chair of the new body, Public Health England and, crucially, a "commencement" clause put down by Labour. It seeks to delay the introduction of much greater competition in the NHS in England until 2016 from Lansley's intended date of 2012.

MPs will also get a chance to debate the bill on Tuesday afternoon when they examine a separate Labour motion. But to cause any last-minute delay to the bill Labour needs Liberal Democrat parliamentarians in either house to rebel, which is unlikely. Barring unforeseen events, the bill is expected to gain final parliamentary approval on 20 March.