MP for Mid Worcestershire Peter Luff wrote his plea after meeting with a group of field vegetable and salad growers in his constituency.
He learned that, like many soft fruit growers across the UK, they are struggling to find sufficient labour this summer and have already been forced to let their produce go to rot.
His letter stated: "I am clear that it is time for the Government to take urgent action to prevent the loss of significant parts of the British horticulture industry and a consequent reduction in our food security at very difficult international times.
"We urgently need to re-open SAWS - which is a temporary scheme for migration of agricultural students to the United Kingdom for a period of six months - to all the countries which once benefited from it."
He is now seeking an urgent meeting with the home secretary to explain his concerns.
For decades the SAWS scheme allowed UK growers to hire foreign workers from outside the EU to help with seasonal work.
This year, however the Government has restricted it to workers from just Bulgaria and Romania - both of which have recently joined the EU. It has also been restricted from 25,000 workers to 16,250.
Both moves are part of plan to phase out SAWS completely by 2010, in order to prevent the kind of high-level immigration experienced in the UK the last time a group of eastern European countries joined the EU.
Luff pointed out this plan is backfiring and actually attracting more EU immigrants into the country.
He said: "Growers are seeking to recruit staff from other eastern European countries such as Poland, Slovakia, Lithuania and so on.
"These staff members, when they arrive in the UK, discover that the work is more demanding and less well-paid than they had imagined and move on elsewhere in the economy. They then build relationships, professionally and personally, and are much more likely to settle down in the UK as a result.
"The agricultural students who came in under SAWS could only come for six months and all returned to their native countries, leaving behind them only happy memories and taking with them the proceeds of their work."
Executive director Christine Lumb of Concordia, which provides growers with labourers from SAWS, also met with the MP.
She told Grower that the shortage of workers is being made worse by the fact that vegetable picking has lost its appeal among EU workers: "In the past, it has always been fairly easy to source labour for vegetables because the young men regarded it as more of a 'man's job' - but even the young men are not there this year."
She added: "One tomato grower in the area said that 20 per cent of her workforce has left - even though they were on good money.
"Another grower was using illegal labour because he couldn't get SAWS workers and couldn't source EU workers. It's a really sorry tale."
She said the reason the meeting was called was that "we have not been able to provide one of the growers that has been with us for many years with the total number of SAWS workers he wanted".
She added: "He - like many people - has had to mix SAWS with EU workers. This year we have had to make up a considerable amount of labour with EU workers."
Paul Southall, partner at vegetable grower D Southall & Sons, who also met up with Luff, said his business was not too badly affected but added: "Some pea and salad growers in the region are struggling to get their crops harvested. It's an issue."
Other growers at the meeting declined to comment.