Philip Bujak said he had hoped that the move towards greater freedom for schools would be extended to the under-fives and was disappointed that the sector had been 'overlooked'.
'We had hoped that "free schools" would extend down to nursery level,' he said. 'What is there for the nursery sector? The focal point should be at the start.'
He said that the plans seemed to suggest a view that 'education doesn't start until you're five'.
Government plans to allow parents to apply for state funding to open their own schools do not extend to letting parents open their own nursery schools, and the invitation for primary schools to become academies does not include maintained nursery schools.
However, nursery and infant schools, which cater for children from three to seven years old, are able to apply for academy status.
Mr Bujak said that Montessori nurseries were 'largely private, but not through choice', because Montessori teaching methods had not been accepted by the state sector.
Mr Bujak also revealed that plans for the MSA to open the first Montessori state primary school - to be run by a local authority but with funding for the building and training provided by the MSA - received a setback last week (News, 10 February).
The proposal was rejected by Barking and Dagenham council in London. It was turned down because Montessori teachers are not considered to be 'graduate' teachers.
'We're looking for a local authority to have a bit of vision,' Mr Bujak said. 'It's very shortsighted.
'There are two other local authorities we are having discussions with,' he added.