Almost half of local authorities providing language lessons in primary schools say they can only guarantee continued support for the next six months, while one in six admits they are already in decline.
A survey of 100 authorities, by languages organisation Cilt, reveals the fragile state of primary languages as uncertainty over their future status and funding continues.
Languages were due to be made a statutory part of the key stage 2 curriculum from September 2011, but the legislation was ditched in the "wash up" process before the general election. The Government has said it will review the whole curriculum.
Therese Comfort, head of primary languages at Cilt, said: "There is an overwhelming demand for clear policy direction on languages to ensure that language teaching continues in primary schools. We have come a long way in the past five years, but we need a long-term commitment. The worry among local authority advisers is that without it the momentum will be lost."
Of the 100 authorities that took part in the survey, 17 were no longer maintaining the same level of support for primary languages, while 38 would only guarantee funding until March.
All advisers surveyed said at least four out of five schools were offering languages, and in one in three authority areas languages were taught in every primary school. National research has shown that 92 per cent of schools now provide languages within class time - compared with just 20 per cent in 2000.
But the advisers reported that headteachers were becoming hesitant to commit time, staff and money to primary languages.
One said: "One school has decided not to continue. Three others are reluctant or unsure. The vast majority are very keen to continue if the support continues."
Although some headteachers said they would continue with languages "no matter what", 83 advisers said that language teaching should be made statutory in primaries.
Janet Lloyd is a languages strategy consultant in Warrington, where all 71 primaries teach languages to all key stage 2 children. She said: "It would be really sad if statutory status was not achieved.
"Our teachers have come to twilight meetings, they have extra training, they do additional after-school work. They all deserve the chance to prove primary language teaching works."
Insight, page 38.