MPs were outraged last night after ministers published controversial plans to build thousands more West homes as Parliament went into its lengthy summer recess.

Communities Minister Baroness Andrews announced a consultation on how many new houses are needed in the South West by 2026.

She has added more than 23,000 additional houses to the previous total of 569,450 – which many campaigners felt was far too high already.

There are warnings of slowing demand because of the property slump, and concerns over how many of the new developments will be in the flood plain.

Opposition MPs joined forces to condemn the way the Government's proposed changes to the regional spatial strategy (RSS) were made public.

The former Avon bears the brunt of the additional homes, with Bristol's total rising from 30,000 to 38,500, while South Gloucestershire is earmarked for an extra 2,000 and Bath and North East Somerset another 500.

Although more new housing was not imposed on other parts of the West yesterday, there have already been steep increases since the original RSS was published three years ago.

So although Gloucestershire's total remained at 7,800, that was up 7,800 from the original document, and it is a similar story right across the West.

The Government said the 29 per cent increase in homes was needed because the region was the only one to have above average property prices and below average incomes, and increased the affordable housing target to 10,000 a year, 35 per cent of the total.

It forecasts more than 28,000 new households will form every year in the region up to 2026, and optimistically predicts the economy will grow at 3.2 per cent annually, delivering 484,500 jobs.

Ministers say development should focus on Bristol, Bath, Cheltenham, Chippenham, Swindon, Salisbury, Dorchester, Gloucester, Weymouth, Taunton and Weston-super-Mare.

Baroness Andrews said: “Beyond the short-term squeeze of the credit crunch, the number of new households are still outgrowing the number of homes being built – not least because our society is ageing and more people are choosing to live alone.

“In a rural region known for its quality of life, if more homes are not built now the housing ladder will get even further out of reach, leaving the next generation with nowhere to live further exacerbating the real problems in the South West.”

She also claimed it was important to give all those interested a chance to comment – but critics said that would be difficult as the 12-week consultation runs through the summer holidays.

Liberal Democrat environment spokesman Steve Webb condemned the Government for “sneaking out” the plans, which they were sent back in January.

He said: “It is an outrage that the Government has sat on this document for six months and now plans to run a consultation over the summer – people could be forgiven for being cynical about the Government's motives.”

The Northavon MP told the Daily Press the “fantasy figures” came with the housing market collapsing, and bore no relation to what was really needed.

The original proposal for South Gloucestershire was for 23,000 new homes to be built. Mr Webb said for the Government to increase it to 32,800 was “totally unacceptable” and “simply madness”.

Bath Lib Dem Don Foster said the Government had gone “barking mad”, warning two-thirds of the district was either green belt or in an Area of Outstanding Natural Beauty. He said the total was even more bizarre because it did not include new student accommodation being planned by the city's two universities.

The Conservatives said the plans – “rushed out” among 30 statements on the last day of Parliament – would lead to valuable green belt land being concreted over. Shadow Communities Secretary Eric Pickles said the Bristol-Bath, Cheltenham-Gloucester and Dorset Green Belts would be “ripped up” with the end result being “urban sprawl into the countryside”.

He said: “I fear that Labour's plans harm quality of life, ruin picturesque parts of the countryside and push up carbon emissions – letting rip with the bulldozer and concrete mixer, Labour are building the sink of estates of the 21st century.”