The Lib Dems have pledged an extra £1bn a year for nature-friendly farming schemes and to ensure future trade deals meet UK food standards as they seek to appeal to rural voters.

The Liberal Democrat also focus on the “national sewage scandal” which has prompted widespread public concern in recent months, as part of an election manifesto containing a raft of environmental measures.

The party is pledging to transform water companies into “public benefit companies”, ban bonuses for bosses until leaks end, introduce a “sewage tax” on company profits and give local environmental groups a place on boards.

There are also plans to set legally binding targets to prevent sewage dumping into bathing waters and sensitive nature areas by 2030, and enforce laws to make sure storm overflows – which can put untreated sewage into waterways and seas during heavy rain – operate only in exceptional circumstances.

As the party positions itself as the alternative to the Tories in many rural constituencies, the manifesto also attacks the Conservatives’ “botched” moves away from EU-era farm subsidies and post-Brexit trading arrangements.

Liberal Democrats leader Sir Ed Davey during the party's General Election manifesto launch at Lumiere London  (Image: Press Association)

So there is an extra £1bn a year for the environmental land management schemes (ELMS), while the manifesto says it will support farmers “properly” to restore woodland, peatland and waterways, including creating natural flood protections, boosting wildlife and storing carbon while producing food.

For farmers there is also a pledge to maintain high welfare and environmental standards and ensure future trade deals have to meet them, so that British producers are not being put at an unfair disadvantage.

And the Lib Dems are pledging to negotiate “comprehensive veterinary and plant health agreements” to give farmers the ability to trade with EU countries with minimal need for checks.

Elsewhere in the countryside, the party is pledging to plant at least 60 million trees a year, double the size of the network of protected natural areas, significantly increase the amount of accessible green space, and explore a “right to roam” for waterways.

They say they want to ban the use of horticultural peat and the routine burning of heather on peatlands and protect the country’s temperate rainforest as part of efforts to use nature to help tackle climate change.

Climate measures also include a ten-year emergency upgrade programme for homes, with free insulation and heat pumps for low income families, investing so renewables generate 90 per cent of UK power by 2030 and bringing overseas aid back to 0.7 per cent of national income with a focus on climate change.