Ms Smith ousted Tory Eric Ollerenshaw by 1,265 votes in Thursday night’s General Election.
The count at Salt Ayre Sports Centre went on through the night with the result announced shortly after 8am on Friday morning following a bundle recount.
Ms Smith said afterwards: “It’s quite overwhelming.
“I think it’s a really positive message and we ran a really positive campaign.
“The first thing I’m going to do is go to sleep! Then, I want to be a really positive MP who is part of the Lancaster and Fleetwood communities.”
Outgoing former MP Eric Ollerenshaw said: “I want to thank my supporters who have fought a long hard battle. I hope I haven’t let you down.”
UKIP came third after picking up strong support particularly in Fleetwood.
Matthew Atkins, the UKIP candidate, said: “Fleetwood is usually where we have a bigger vote share.
“There is a lot more dissatisfaction with working people who work in the traditional industries and no longer have a voice, not just the fishing industry but North West industry generally.
“People in Fleetwood don’t think the two main parties are offering them anything.”
Robin Long, the Liberal Democrat candidate, was not present for the declaration because his wife is eight months pregnant and they had a midwife appointment.
Northern party candidate Harold Elletson was also not present.
Full results: Smith 17,643, Ollerenshaw 16,378, Matt Aktins (UKIP) 4,060, Chris Coates (Green) 2,093. Robin Long (Lib Dem) 1,390, Harold Elletson 174.
The total number of votes cast was 41,738 with a turnout of 66.93%.
Chris Coates, the Green candidate, said high turn out was due to a combination of it being a nice day and the fact that a closely-fought election had galvanised people to vote.
Nationally, the Conservatives are predicted by exit polls to be the largest party.
They were predicted after polls closed on Thursday to win 316 seats to Labour’s 239 but on Friday morning experts were saying the Tories could win enough seats to gain an overall majority.
By 9am, 630 out of 650 seats had been declared, Conservatives 315, Labour 228, SNP 56, Lib Dems 8. They were predicted to win 316 seats to Labour’s 239.
The Scottish National Party were having a great night after wiping out many Labour strongholds in Scotland, while it was turning into a bad night for the Lib Dems with cabinet members Vince Cable and Ed Davey losing their seats, as well as veteran MP Simon Hughes.
David Cameron, on retaining his Witney seat, said: “I want my party and I hope, a Government I’d like to lead, to reclaim the mantle of one nation, one United Kingdom.”
Ed Miliband, leader of the Labour party, on holding his Doncaster North seat, said: “This has been a very difficult and disappointing night for the Labour party.”
Nick Clegg, leader of the Liberal Democrats, said on holding his Sheffield Hallam seat: “This has been a cruel and punishing night for the Liberal Democrats.”
Nicola Sturgeon, leader of the SNP, said: “The tectonic plates of Scottish politics have clearly shifted.”