Housing Secretary Steve Reed says his job should be “on the line” over a pledge to build 1.5 million new homes in England – but two leading experts have told BBC Panorama the government looks set to miss its target.

Prof Paul Cheshire, who has advised previous governments on planning policy, said there was “absolutely no way” it would succeed.

Meanwhile, Neil Jefferson of the Home Builders Federation, which represents private housebuilding companies, warned the government’s target was “looking increasingly distant”.

But Reed insisted he would “absolutely” meet the goal and told Panorama the widespread scepticism would make “celebration all the sweeter” when he hit it.

The promise to build the homes over the next Parliament, which is due to run until 2029, was a cornerstone of Labour’s manifesto.

“My job should be on the line if I fail to meet my target,” Reed said. “I expect to be held to account.”

But Mr Jefferson has told Panorama housebuilding is “flatlining” at about 200,000 new homes a year, instead of the 300,000 annually required by the target.

A cumbersome planning process, environmental regulations and skill shortages – among other issues – were impacting the industry’s building rates, he said.

Many big or controversial planning applications are currently decided not by trained council planning officers, but by elected local councillors on planning committees.

This means national priorities like building more homes often clash with local opposition.

Councils are also supposed to adopt a “local plan”, a document outlining where development should happen and how it aligns with national policy. These plans can help to streamline planning approvals – if a proposal fits the plan, it should get permission unless there is a strong reason to reject it.

This means these documents are controversial, and can often face fierce local opposition.

Fewer than a third of councils currently have an up-to-date local plan in England, according to the Planning Inspectorate.

But Reed told Panorama the government will soon force councils to adopt a local plan.

Under proposed changes, councils will have to produce a plan within 30 months of starting the process – instead of the current average of seven years.

The government has also announced it will boost funding and training for planning authorities to help them with their plans.

Reed insisted government reforms would help developers build more homes, including mandating new housebuilding targets for councils and “more powers” for him to call in – or review – “unreasonably” rejected housing development schemes.

Reforms to the rules governing protected green belt land, which makes up 12.5% of land in England, have also been suggested by the government.

The first green belt was created in the 1930s, to try to stop cities from sprawling into the countryside. But many sections of green belt today contain intensive farming units, industrial buildings, quarries and golf courses.

The government has come up with a new concept called the “grey belt”. The aim is to make it easier to get planning permission for green belt land that is considered low quality or has already been built on.

However, the government has left it up to each local authority to decide which sites qualify locally as grey belt.

Prof Cheshire, a former economist at the London School of Economics, said this was a missed opportunity: “If the grey belt had been defined in a legally watertight way… then it would have been cut and dried and you could have built a lot of houses, but they didn’t do that.

“They left it to the fuzziness of the planning system and therefore to local lobbying, and… it won’t happen”, he said.

For Prof Cheshire, the government’s reforms are “not going to make much difference”. He added that “there’s absolutely no way that we will build 1.5 million houses”.