The Welsh Conservatives’ “successful brand” was marginalised by the wider party during the general election, Andrew RT Davies has claimed.
The Welsh Tory leader said the campaign had been “confusing” with London-only messages allowed “to take centre-stage”.
The party lost three Welsh seats to Labour at the general election.
A Westminster Tory source said there was a Welsh campaign in the assembly elections: “We still went backwards.”
His criticism comes a day after Mr Davies claimed the Welsh party lacked clear leadership.
Mr Davies is widely known as Welsh Conservative leader but under party rules, his authority does not extend beyond the National Assembly Tory group.
Despite some early expectations that the party could become the largest Welsh force in Westminster, the party’s overall seat haul total in Wales fell to eight, with Labour solidifying its position as the largest Welsh group at Westminster with 28 MPs.
The Tories lost their overall Commons majority, losing 13 seats, as the Jeremy Corbyn-led Labour party gained 30 seats across the UK.
Mr Davies said: “There are no prizes for coming second in politics, we know that only too well, having outperformed expectations in many Welsh seats on Thursday without doing enough to win them.
“Jeremy Corbyn would do well to remember that his party came a distant second in this election.”
But he said: “There is no getting away from the fact that this was a bad day at the office for the Conservative Party.”
He said Welsh Labour “were able to fight a local campaign; hiding Jeremy Corbyn from all of their literature during the early days of the campaign – and yet still able to benefit from a late surge in his popularity nationally”.
“Meanwhile, the left wing vote in Wales coalesced around Labour, with the nationalists and Liberals haemorrhaging support in most seats,” he said.
“Sadly, the decision to allow the UK messaging to marginalize our own, successful brand of Welsh Conservatism meant that we were not in a position to capitalise on those shifting sands in Welsh politics.”
He added: “We are proud unionists but we cannot keep fighting general elections without acknowledging the need for distinctive messaging.
“Health and education have been devolved to the Welsh Assembly for many years and the decision to allow London messaging to take centre-stage only confused our offering.”
He said the Welsh Conservative local election result, when the party gained 80 seats, was proof that “locally driven campaigns work”.
However, a Conservative source in Westminster said: “We had a Welsh campaign in the assembly elections, but we still went backwards.”
Last year, the Tories lost three assembly seats when their share of the constituency and regional votes fell by almost four points.
However, a source close to Mr Davies said that in 2016 “London controlled the purse strings” and that the party’s messages were based on polling data gathered centrally.
During the campaign, the AM for South Wales Central had accused Welsh Secretary Alun Cairns of being unwilling to take part in the BBC Wales Leaders’ debate after neither Mr Davies or Mr Cairns decided to take part.
Mr Cairns, who was reappointed as Welsh Secretary on Sunday, had said it was intended Mr Davies would appear on the programme.