Environmental experts have expressed "frustration" at funding issues which have held up tests for radioactive particles on the Solway coast.
Sellafield Ltd is in talks about its monitoring programme
The Scottish Environment Protection Agency hoped to test for pollution from Cumbria's Sellafield plant in August.
However, it has been unable to secure full funding from the agencies responsible for the English site.
A spokesperson for Sellafield Ltd said it was in talks about whether it needed to extend its monitoring arrangements.
The Nuclear Decommissioning Authority - which owns the site - has offered to meet 60% of the £100,000 costs.
Sepa has approached Sellafield Ltd - which runs the plant - to meet the funding shortfall but without success.
The environmental group's radioactive monitoring expert Dr Paul Dale said he believed these additional checks were necessary.
Earlier this year Sepa was alerted by its English counterpart - the Environment Agency - about an increase in the number of radioactive particles on beaches in North Cumbria.
It wants to check for any similar problems in Scotland and has identified sites at Powfoot, Southerness and Kirkcudbright to carry out the tests.
Mr Dale said it was import to assess if there was "any identified risk to public health and the environment from any Sellafield-originated radioactive particles".
Sepa wants to carry out additional checks on the Solway
"To enable this, we had all the essential preparation completed by early August, so our contractors could begin later that month," he said.
"However, due to funding issues, this has not been possible, and Sepa is frustrated that these funding issues have continued to delay this necessary work."
Dr Dale said that radioactive monitoring was funded under the "polluter pays" principle.
He said Sepa was working with the EA to try to force Sellafield Ltd to meet the funding requirement.
"The important point is that monitoring should not be delayed further, and any risks identified are assessed," he said.
An NDA spokesman stressed that regular monitoring already took place in the area due to the proximity of the Chapelcross plant in Annan.
"What they are talking about is using a particular type of vehicle," he said.
"This is extra monitoring on top of the normal monitoring we have conducted."
He confirmed that the group had offered £60,000 towards the total costs of the monitoring.
A spokesperson for Sellafield Ltd said it was currently in talks about the situation.
"Sellafield Ltd carries out a comprehensive annual monitoring programme in line with that which is required by our regulators," she said.
"We are currently in discussions with the EA as to whether there will be an extension to this programme."