But his abrupt departure came in for criticism, with one Tory councillor tweeting: "Hartlepool's Labour candidate Paul Williams petulantly refusing to make any comments and thank the staff, police, and his volunteers is really graceless".
Ahead of May 6's vote, the Survation poll for ITV's Good Morning Britain put the Conservatives on 50% - 17 points ahead of Labour in a seat which has remained red for 57 years in its current and previous guise.
And Starmer had played down expectations for Labour, stressing "I never thought we would climb the mountain we have to climb in just one year".
"This is a historic result", said Tory vice president Amanda Milling in the first response.
It was a dramatic count at the English Institute of Sport that saw Sheffield Labour not only lose control of the council after a decade but lose its leader Bob Johnson who failed to defend his seat in Hillsborough.
Labour's choice of Mr Williams, an anti-Brexit candidate whose vocal support for a second referendum has been blamed for the loss of Stockton South - a seat that voted by over 60 per cent to leave the European Union - has been criticised given Hartlepool voted to leave by an even bigger margin.More news: Statement on AstraZeneca COVID-19 vaccine following JCVI update
Labour leader Keir Starmer has made a point of moving the party from the left toward the center of United Kingdom politics, espousing more nationalist policies, hiring allies of former Labour Prime Minister Tony Blair and promising to break with his left-wing predecessor Jeremy Corbyn.
Senior Tories called the Conservatives the "true workers" party' last night after a series of astonishing electoral gains.
CWU polling in Hartlepool had predicted the Labour defeat while revealing widespread support for raising public-sector pay and extending public ownership, including by renationalising Royal Mail.
Starmer has tried to shift his party towards the centre ground after two defeats under the left-wing leadership of Jeremy Corbyn.
Across the United Kingdom, more than 5,000 seats were up for grabs in the voting on Thursday.
Labour's struggles in Scotland were also expected to be laid bare, with Nicola Sturgeon's Scottish National party forecast to retain power.More news: France threatens to cut electricity to Jersey over post-Brexit rules
Scotland has been part of the United Kingdom since 1707 and the issue of Scottish independence appeared settled when Scottish voters rejected secession by 55%-45% in a 2014 referendum.
They suggest Mr. Starmer faces an increasingly daunting task to unseat Johnson at the next general election due in 2024.
Depending on the latest results, calls for another referendum could increase tensions between Edinburgh and the United Kingdom government in Westminster.
"It's quite clear when we see the ballots land on the table today, that we haven't been able to catch enough of those numbers to get us over the line today", shadow transport secretary Jim McMahon despondently told the BBC.
Some 129 members of the Scottish Parliament are to be elected, along with 60 members of the Welsh Parliament, known as the Senedd.
The election result from Scotland's vote could have the biggest UK-wide implications.More news: US backs waiving intellectual property rules on vaccines