Jenny Willott MP and Mike German at the manifesto launch in Cardiff

It includes a target to produce all electricity from renewable sources by 2050 and proposals to give grants and free advice to families to "go green".

The party's health plans include a guaranteed standard for NHS service, "health hubs" and "walk-in centres".

Healthier school meals and smaller primary class sizes are also proposed.

In the introduction to the 60-page manifesto, "A Fair Green Future," Mike German, who leads the party in the assembly, said they had the "energy, drive and ambition" to use new powers devolved to Wales to "make the assembly work for the people".

The document describes the environmental plans as "bold but achievable".

LIBERAL DEMOCRAT POLICIES 100% renewable electricity by 2050 Health hubs and nurse-led walk-in centres Smaller primary school classes 500 extra police community support officers Cut red tape for business Better integrated public transport Re-introduction of the Post Office Development Fund Source: Welsh Liberal Democrat manifesto

The party wants 30% of Wales electricity to come from renewable sources by 2020, as a "milestone target" towards all electricity being renewable by 2050.

Measures to achieve the targets include making all new buildings carbon neutral by 2015, requiring public buildings to generate more of their own energy and insulating homes better.

The manifesto also promises to oppose the building of nuclear power stations.

'Dental deserts'

To improve NHS care the party proposes "nurse-led walk-in centres".

The centres would offer "simple and straightforward access to treatment" seven days a week and be based alongside larger accident and emergency departments and GP out-of-hours services.

Lib Dems propose bringing together services such as GPs, physiotherapists and pharmacies with housing and social services to form "health hubs". There are also policies to make it easier to register with an NHS dentist.

More salaried dentists and increasing the use of mobile dentists are two Lib Dem plans to help parts of Wales the manifesto describes as "dental deserts".

"A really serious comprehensive plan for government" Jenny Willott MP, campaign chair

The document promises to legislate to improve carers' rights and to place a duty on the NHS to consider their welfare.

Education priorities include reducing primary school classes to an average of under 25 and investing more money in school buildings.

The party also pledges to give all pupils healthier meals and guarantees to maintain the extra financial support Welsh students currently receive.

The manifesto confirms plans announced at their Welsh conference to fund an extra 500 police community support officers.

There are also promises to "free business from unnecessary red tape" and to make a "massive injection" in social housing.

'Backbone'

Jenny Willott MP, who is chairing the party's election campaign, said it was a "really serious comprehensive plan for government" which would show how the Lib Dems would "make the most of the assembly and what it can do for the people of Wales."

The Cardiff Central MP said it offered the strongest green programme of any party, with "no half-measures."

The Lib Dems still refused to say, however, which of their proposals would be priorities if they were in coalition talks after the election.

Mr German said that last time they were in coalition, with Labour from 2000 to 2003, more than 100 Lib Dem measures were passed. He said that figure would be "a benchmark this time."

The party says it would fund its ideas with at least �600m which it estimates will be available in the next assembly term for new spending.

Mr German was repeatedly pressed on Lib Dem terms for coalition, but he refused to go any further than the party's previous stance: that it was prepared to form a coalition with any other party as long as Lib Dem policies formed the "backbone" of a government programme and it was not a step to independence.

With six AMs, Lib Dem formed the smallest group in the assembly chamber after the 2003 election.