Head teachers and MPs in the Westcountry have rejected claims that children in parts of Devon and Cornwall are being let down by schools.
Shadow education secretary Stephen Twigg said the isolation of northern towns and coastal resorts such as Torbay was an obstacle to recruiting talented teachers and heads.
Mr Twigg blamed the "long-term decline" in seaside holiday resorts and said too many schools in those areas had failed to match the improvements in results elsewhere.
He told an invited audience at the House of Commons this week that the problem was "blighting the life chances of thousands of children and young people" and urged a series of "regional challenges" to raise standards.
The National Association of Head Teachers said it did not recognise the analysis.
Ian Bruce, the union's national executive in the South West, said: "Cornwall's results are in line with and above the national average so it seems strange Mr Twigg would make any connection to the region.
"The area's head teachers are extremely committed and would balk at any suggestion of complicity in such underachievement."
Mr Twigg claimed that fewer than half of all pupils in places affected get five good GCSE grades A* to C, including English and maths, and do not make the progress you would expect of pupils.
He called for the number of graduates recruited to teach in challenging areas under the Teach First scheme to be doubled to 2,000 a year.
He said: "While overall results improved between 2006 and 2010 coastal areas fared less well.
"If you take Cornwall, the probability that a poor child will have GCSE results in the bottom quarter nationally increased by 8% between 2006 and 2010."
Liberal Democrat MPs representing coastal towns reacted with anger and puzzlement at the claims.
West Cornwall MP Andrew George, said Labour had chosen to "pump money into the cities and Labour heartlands", leaving others to struggle.
"Rather than talking down the efforts of the schools in Cornwall, Labour should have listened to our campaign for fair schools' funding," he added.
Adrian Sanders, MP for Torbay, said he was "not aware of any recruitment problems" among teachers.
"There has been a long standing aspiration problem reflective of the weak economy which we are hoping to change with better investment in the economic infrastructure locally," he added.
"We have some of the best performing schools that select the brightest and best from a wide geographic area at 11 and some that do a magnificent job given their intake but are never likely to be able to compete with most mixed ability comprehensive schools."