But senior Labour figures insisted the record-low, 23 per cent turn-out in England and Wales meant the Tories could not claim public endorsement for their Eurosceptic campaign. And they denied the results would set back Tony Blair's plans to take Britain into the single currency soon after the next general election.
Mr Hague went into the fight knowing that a poor performance would put his job on the line. In the event, he turned the tables on Labour, which must now conduct a painful inquest into what some party insiders call its "non-campaign".
Far from suggesting that the Tories could actually lose seats at the next general election, as the party feared two months ago, the Euro results will send a shiver down the spines of Labour MPs once they have totalled up the votes cast in their own constituencies.
"A lot of us will be feeling very uneasy," one Labour backbencher admitted yesterday. "In many areas, the Tories or Lib Dems will be able to claim the sitting Labour MP no longer has a mandate because Labour was not in first place."
Some Labour sources said the party played into Mr Hague's hands. Robin Cook, the Foreign Secretary, had argued for Labour to play up European issues, but was overruled by cabinet colleagues who insisted that the voters were "not interested in Europe".
Mr Hague seized his opportunity, toughening his line against the single currency without formally changing his policy of not joining it in this Parliament or the next. He was convinced that people who opposed European integration were more likely to vote in the Euro elections than pro-Europeans or the many people who simply didn't care.
Tory private polling suggested that many Labour and Liberal Democrat supporters were much cooler about Europe than Mr Blair and Paddy Ashdown. A string of opinion polls reinforced Mr Hague's determination, suggesting that opinion was hardening against the euro. But Mr Hague's strategy was high-risk, since the party's Europhiles, led by Kenneth Clarke and Michael Heseltine, believed they had secured a truce under which the party would play down the single currency.
Although the Tory "big beasts" kept their heads down during the campaign, they will now seek their revenge. Provided that Mr Blair gives a lead, Mr Clarke and Mr Heseltine are expected to join the embryo "Vote Yes" campaign on the euro next month, reigniting the Tory civil war on Europe. But they are furious with Mr Blair, too, for failing to show leadership on the issue during the Euro election.
Margaret Beckett, Labour's campaigns co-ordinator and the Commons leader, symbolised the party's low-key approach by taking a week's holiday during the three-week campaign. That has angered many Labour colleagues, and prompted speculation she will be sacked as campaigns chief when Mr Blair reshuffles his Cabinet next month.
Labour officials admitted that their drive to warn voters that supporting the Tories would "let them back in" misfired because people did not see Mr Hague as a threat. "They just laughed at us," said one.
Labour sources suggested that the party may have taken the voters for granted. "A lot of people thought we could afford to sit back; it should be a salutary lesson," said one insider.
Some cabinet ministers, including John Prescott, the Deputy Prime Minister, believe that the disastrously low turn-out in Labour's heartlands cannot be explained by a "culture of contentment" with the Government - the excuse cited by Labour headquarters.
They are increasingly worried Mr Blair's message is too focused on Middle England, rather than on the working class. "These results blow a hole in the Blairites' claim that our people have nowhere else to go," one cabinet minister said last night. "They can stay at home - and they can do that at the next general election, too."
The prospects of Mr Blair calling a referendum on reform of House of Commons elections have also receded. Opinion among Labour MPs appears to be hardening against proportional representation, which denied Labour an overall majority in the Scottish Parliament and Welsh Assembly and failed to prevent a drubbing in the Euro poll, the first time it has been used in a nationwide election in Britain. "MPs who are fairly neutral about the idea have seen the damage PR can do," said Fraser Kemp, the MP for Houghton and Washington East.
The Make Votes Count campaign, which supports reform, said the "nervousness" about PR would settle down once MPs saw the Lib-Lab coalition in Scotland working. But cabinet ministers opposed to PR believe the nervousness now extends to Downing Street.Reuse content