A former health minister has warned the Government's controversial childhood obesity strategy is unlikely to succeed amid anger among campaigners that promised measures to curb unhealthy sugar consumption had been "watered down".

Conservative MP Dan Poulter, a hospital doctor who was a minister in the last parliament, said the document was not the "game changer" promised by Health Secretary Jeremy Hunt with a "worrying lack of practical measures".

His intervention came amid reports Theresa May had overruled Mr Hunt, ordering the removal of restrictions on advertising and promotional deals on junk food amid fears they could hit employment in the food industry at a time when the economy was faltering.

Speculation of a rift was heightened by the decision to release the document in the middle of the Commons summer recess while both Mrs May and Mr Hunt were out of the country.

No health minister was made available for media interviews and it was left to Financial Secretary to the Treasury Jane Ellison - who helped draw up the strategy in her previous role as public health minister - to do the rounds of the broadcast studios.

The Department of Health insisted the decision reflected the fact that it was a cross-government programme while Ms Ellison denied that it had been downgraded as a government priority since Mrs May came to office last month.

"No, that's not right," she told the BBC Radio 4 Today programme.

She acknowledged, however, that ministers had considered "a whole range of policies" over the past 12 months and that the final plan was not as "iconic" as taking action on junk food advertising would have been.

The strategy confirmed the Government would go ahead with the "sugar tax" on soft drinks announced by former chancellor George Osborne, but relies on voluntary action by the industry to reduce unhealthy sugar levels in other products aimed at children.

Dr Poulter said that such an approach was unlikely to achieve the kind of reductions that were needed.

"This is certainly not the game-changing plan for reducing childhood obesity that it had been built up to be," he said.

"Many of these measures, such as support for school sports, sound good, particularly during the Olympics, but there is a worrying lack of practical measures about how we can turn warm words into reality.

"Looking more closely at some of these plans, I have concerns, because when we draw on learned experience of corporate behaviour, we know that the continuation of a policy of hoping that sugary drinks and junk food manufacturers will want to start working with government to drastically reduce unhealthy sugar content is unlikely to be successful."

Liberal Democrat leader Tim Farron said the strategy should be based on evidence of what works not "vested interests of ministers or the lobbyists from the junk food industry".

He added: "I have to wonder where is the Health Secretary and why it is not him launching this much-delayed report."

Even Sainsbury's chief executive Mike Coupe described the strategy as a "first step", warning that a far more wide-ranging approach was needed.

"We need a holistic approach to tackle childhood obesity, including compulsory measured targets across all nutrients - not just sugar - and mandatory traffic light labelling across all food and drink products, regardless of whether they are consumed inside or outside the home," he said.

Celebrity chef and healthy eating campaigner Jamie Oliver said ministers had missed an opportunity to reverse the "tide of diet-related disease".

"With this disappointing and, frankly, underwhelming strategy, the health of our future generations remains at stake," he said.

Ms Ellison however insisted the Government had adopted the most effective measures recommended by experts to bear down on sugar consumption.

"That is the most ambitious programme of reformulation that any developed country has undertaken," she said.