The fate of some rare slow worms is likely to slow development of 110 new homes in the Birmingham district of Yardley.

The the legless lizards have become the latest subject of contention as residents resist brownfield development. And if the House of Lords leaves the government’s Environment Bill unamended at its sessions next week, the story of the Yardley slow worms could be repeated nationwide.

New biodiversity requirements introduced by the bill could damage the viability of brownfield development and cost local authorities to implement, with the environmental impact being questioned by some.

The bill returns to the floor of the House of Lords next week. This is the last serious opportunity to make amendments to The Environment Bill, which contains a new biodiversity net gain condition for planning permissions.

The bill extends biodiversity protection to potentially all sites, not just those listed as sites of special scientific interest.

To meet this requirement, developers will need to measure biodiversity gains using a biodiversity metric. The metric is already published in draft, and it will be formally implemented when the net gain requirement takes effect, probably in 2023.

The biodiversity metric is a habitat-based approach used to assess an area’s value to wildlife. The metric uses habitat features to calculate a biodiversity value. The biodiversity metric calculates how a development, or a change in land management, will change the biodiversity value of a site. For example, building houses, planting a woodland or sowing a wildflower meadow.

The new metric replaces earlier codes prepared by Natural England. It discourages off-site mitigation and encourages on-site action.

The British Property Federation has broadly backed the biodiversity metric as clear and transparent, but housebuilders are not so sure.

The Home Builders Federation warned that the metric produced a higher baseline requirement for diverse brownfield land than the fairly limited diversity found on many arable greenfield sites. The result would be more expensive off-site mitigations, or setting aside more land for on-site mitigation, both of which will affect viability, Planning Resource reported.

The metric has also met criticism from environmental and ecological groups, who fear it condemns too much land as “degraded” and therefore not worthy of protection. Complaints include failure to distinguish scrubland with low value from high-value scrub that supports birds like nightingales and turtle doves. The Chartered Institute of Ecology and Environmental Management said the metric needed a report, Ends Report said.

The House of Lords is due to consider amendments on Monday 13 and  Wednesday 15 September.