SNP leader Nicola Sturgeon said she was "bursting with pride" as she joined her party's newly-elected MPs to mark its landslide election victory in Scotland.
The 56 new Westminster members posed for photographs with their party's leader in South Queensferry, overlooked by the Forth bridge.
Ms Sturgeon said ending austerity would be the first priority for SNP MPs.
Meanwhile, former SNP leader Alex Salmond said Scotland was closer to independence after the party's success.
The SNP celebrated unprecedented gains, virtually sweeping the board by taking all but three of the 59 seats in Scotland.
Labour, the Lib Dems and the Conservatives won only one Scottish seat each.
At the event Ms Sturgeon told a gathered crowd of supporters she was "bursting with pride" that so many SNP MPs had been elected.
She added: "The people of Scotland have spoken. They have placed their trust in the SNP to represent them in Westminster as well as Holyrood.
"These 56 SNP MPs will represent the interests of all in Scotland."
In other election developments:
- European newspapers are concerned about the effect on the EU in the light of David Cameron's promise to hold a referendum on leaving. And there is speculation that the Scottish nationalists' spectacular gains may herald the break-up of the United Kingdom.
- Mr Cameron is finalising his first all-Conservative cabinet after his party won a majority in Thursday's election.
- Tottenham MP David Lammy is the first to publicly ponder a bid for the Labour leadership after Ed Miliband stood down
- Pressure is growing on the Scottish Labour leader Jim Murphy after the Unite union called on him to resign.
- Tim Farron and Norman Lamb are among the frontrunners to succeed Nick Clegg after he said he would quit as Lib Dem leader.
- Nigel Farage has recommended Suzanne Evans take over as interim UKIP leader after he said he would step down. Douglas Carswell, the party's one MP, ruled himself out of the running
- Watch BBC election coverage and follow latest reaction
- Read more analysis from the BBC's experts
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Ms Sturgeon called the SNP's victory in Scotland "unprecedented" in UK politics and added: "People voted for an SNP manifesto that had ending austerity as its number one priority. That is the priority these men and women will now take to the very heart of the Westminster agenda.
"It cannot and will not be business as usual when it comes to Westminster's dealing with Scotland.
"My message today to Westminster is this - Scotland's voice will be heard in Westminster now more loudly than it has ever been before."
Ms Sturgeon said she would seek to work with "people of progressive opinion" throughout the UK to put investment in public services and building a stronger economy "at the heart of Westminster".
She ended by thanking the electorate for "placing their trust in the SNP".
"We will not let you down - that is a promise," she said.
The new crop of SNP MPs includes former SNP leader and Scottish first minister Alex Salmond, who won the Gordon seat, and 20-year-old Mhairi Black, Westminster's youngest MP since 1667, who defeated sitting Labour MP and shadow foreign secretary Douglas Alexander in Paisley and Renfrewshire South.
Asked by the BBC's James Cook whether Scotland was now closer to independence, Mr Salmond said the party now had an "overwhelming mandate from the Scottish people to carry forward Scotland's interests", but he added that "the timing of any future referendum" was "a matter for the Scottish people" and that tactics were a question for Nicola Sturgeon".
Elsewhere, Ms Sturgeon said Prime Minister David Cameron had told her he wants to give Scotland more devolved powers as promised by the cross-party Smith Commission following last year's independence referendum.
Ms Sturgeon said she told the PM she did not believe the commission went far enough but she expected to have further discussions with him on the matter.
A Downing Street source denied that the new Conservative government may be considering offering Scotland full fiscal autonomy - full control over all tax and spending.
The denial comes after Tory MP Jeremy Hunt appeared to suggest the opposite on the BBC's Newsnight programme on Friday night.
The Conservative manifesto pledges to implement the recommendations of the Smith Commission, which proposed some further devolution for Scotland.
A senior Conservative source told the BBC: "To be very, very clear we are not considering full fiscal autonomy. We are very clear what we are proposing."
Mr Cameron is spending the weekend finalising his first all-Conservative cabinet after his party won a majority.
The PM has already reappointed Chancellor George Osborne, who has also been made first secretary of state.
Theresa May, Philip Hammond and Michael Fallon retain their jobs at the Home Office, Foreign Office and defence with other announcements due on Monday.