The Green Party has said it will aim to counter “Labour’s message of doom and gloom” as it holds its first party conference since the general election.

The Green conference will begin on Friday in Manchester, kicking off this year’s party political conference season.

At the summer election, the Greens won a total of four seats in Parliament, holding the Brighton Pavilion seat formerly represented by Caroline Lucas, and gaining three other constituencies across a broad swathe of English regions.

As its members gather with swelled parliamentary ranks, the party is expected to call on Sir Keir Starmer to offer a more hopeful message to the public while governing.

Green Party co-leader and Bristol Central MP Carla Denyer said: “As Greens, we counter Labour’s message of doom and gloom. Things can get better – and fast – but only if the new Government has the courage to invest.”

Ms Denyer said she and her party would push the Government to be “braver and bolder”, including on the Budget.

She added: “The Budget at the end of October will set the course for the rest of this Parliament. Green MPs do not accept the need for public spending cuts. On July 4 people didn’t vote for things to get worse. They voted for change, and that’s what we are offering as Green MPs.”

The party will urge Rachel Reeves to adopt a series of tax reforms and rises at the Budget aimed at increasing health spending, carrying out social care reform, and embarking on a nationwide home insulation programme.

Among the tax hikes the Greens propose are a wealth tax on billionaires and multi-millionaires, reforms of capital gains tax and inheritance tax, and closing loopholes in the windfall tax on fossil fuel producers.

Adrian Ramsay, the other Green co-leader and Waveney Valley MP, said: “We need to invest in defending public services and protecting our environment – and we can do so with some changes to the tax system to ask the wealthiest in society to pay a little more.

“These tax changes are modest by the standards of many other European countries who recognise that having high quality public services and a greener economy needs investment.