Wellington was already a Labour stronghold, but this year's election results have tightened the party's grasp on the region considerably.
Notably, National's Chris Bishop lost his seat in Hutt South to Labour's Ginny Andersen in a last-minute swing.
By the time 99 per cent of the votes were counted Andersen had secured a 2229 majority over Bishop.
Just before 10.30pm on election night the difference between the pair was just 110 votes, but a surge a few minutes later widened the gap significantly to 1158.
Robertson said the result was an incredible vote of confidence from New Zealanders.
"I'm extremely proud too of Labour and the fact that we've led people through Covid-19, we've looked after people's lives and their livelihoods, and New Zealanders have believed in us."
During the campaign Robertson said he got a strong and positive feeling from people but he didn't want to count his chickens.
He said he has always known Jacinda Ardern would be an extraordinary Prime Minister and the country has seen that through crises like the March 15 mosque shootings, Covid-19, and Whakaari White Island.
"It's been a really tough period to be Prime Minister and people have seen in Jacinda that leadership that's got huge strength of character, but compassion, razor sharp intellect, they don't come along very often, leaders like Jacinda."
National's party vote was well down in the electorate with the Greens coming in second to Labour at 30.8 per cent.
Chris Hipkins has been the local MP in Remutaka for the past 12 years and has easily secured another three in the job.
He beat National's candidate Mark Crofskey by 17,226 votes by the time 99.1 per cent of votes were counted.
In Rongotai, Labour's Paul Eagle has comfortably secured another term as the local MP, which will be his second after Annette King retired.
With 98.5 per cent of the votes counted, Eagle had a 15,234 majority over Green Party candidate Teall Crossen.
Eagle said he took nothing for granted, but was feeling over the moon.
"Now it's time to deliver, so I've got a strong mandate now to ensure more housing, sorting out our transport, and to focus on climate change and the environment."