More than 60 organisations and individuals have signed a letter addressed to prime minister David Cameron and the leaders of the Scottish, Welsh and Northern Ireland administrations asking them to honour the ELC agreement by showing greater support for landscape and biodiversity issues.
The ELC, signed by the UK Government in 2006, was developed to encourage greater protection, management and planning of landscapes across Europe. Government agency Natural England was appointed to inform local planning authorities on the principles of the convention.
The letter asks the parties to confirm that new landscape legislation will comply with guidelines included in the convention and that Defra's forthcoming natural environment white paper, to be published around April, will centre on the convention's principles.
But former Countryside Commission director Adrian Phillips said many issues concerning nature conservation and biodiversity protection were still being overlooked.
"They haven't figured very highly in recent environmental debate, which has been very much dominated by climate change issues," he added. "Biodiversity in the UK is being threatened in an unacceptable way and we need to do more to protect it."
Phillips said ministers needed to "brush up their acts" and encourage civil servants to take the convention seriously: "Quality of life in Britain depends on - among other things - the quality of the surrounding landscape and you only have to look to realise there is an awful lot that needs to be done."