Prime Minister John Key and Labour Leader David Cunliffe were introduced before an opening karakia was followed by a waiata from Ashburton College kapa haka group.
Peg Noble and Leigh Cleveland were killed and colleague Lindy Curtis was injured when a gunman opened fire at their office on Monday last week.
Several Work and Income staff have dressed in black to pay their respects to their fallen colleagues, hugging each other and holding back tears.
Police officers, St John staff, NZDF representatives firefighters have turned out, along with a crowd of several hundred locals under blue skies and 20C.
Families of the victims were seated close to the front of the stage.
Reverend David Brown of St Andrews Presbyterian Church gave a welcome where he said the incident showed how "the actions of one person can affect and change the lives"of a whole community.
He said that while nothing can "take away the pain and fear"but by coming together as a community, they can find strength.
Ashburton College Phoenix Choir performed 'Anyway' before a reading by local MP Jo Goodhew.
Te Wera King, Arowhenua representative, said the coming together today was to remember the victims but also to release a "sadness lingering over the town". Pastor Rob Davison said Ashburton was "still a great place".
Fear would not intimidate the town, he said, and the town had committed to get through the tragedy together. "You are not on your own," he said.
Ministry of Social Development chief executive Brendan Boyle told the gathering of about 2000 people that injured victim Lindy Curtis is "making progress, to the relief of family and colleagues".
He said the incident highlighted the work of public servants who have committed to helping others.
The victims were helping people in need when they lost their lives, Mr Boyle said.
"They will not be forgotten."
Workers on the front counter of Winz centres must have "empathy, sympathy and a commitment to people", he said.
John Key and David Cunliffe pay their respects at the memorial service. Photo / Martin Hunter
Every step taken to make staff safer was a tribute to those lost, he said.
Mr Cunliffe described today's service as "moving, sombre, a coming together of the Ashburton community in grief around the families of Peggy, Leigh and Lindy".
Mr Key said the service had been very moving.
''It's a very sad day for a tight knit community. It's not the sort of thing you expect to happen anywhere in New Zealand, but you certainly don't expect it in a small town like Ashburton. You can see how close the community is and how much pain they're feeling''.
Mr Key said he had met the families of the victims before the service.
"'They're very strong but obviously there's an enormous amount of pain.
''They reflected to me that they're absolutely feel as though they're getting the support that they require... but it's one of those issues, these things take a long period of time so we need to keep supporting them for a long period of time.''
Mr Key said he hadn't got a sense of bitterness from the families, ''although they'd be fully entitled to feel that''.
''It's just a big hole that's been left and a huge amount of shock.''
Ashburton District Mayor Angus McKay said his message to the town was: "Continue to look out for each other."
He said the incident "does not represent who we are as a community", but rather what defined the community was its reaction, which the mayor says he was proud of.
Mr McKay also thanked police for "making our town safe again".
The hour-long service ended with the singing of the national anthem, and a rousing haka by the Ashburton College kapa haka group.
Ms Cleveland, 55, was laid to rest in Alexandra on Saturday, while Ms Noble was farewelled in at the Ashburton Event Centre on Monday.
Lindy Curtis, 43, who was critically injured in the shooting, has been recovering in hospital.
Russell John Tully, 48, has been charged with two counts of murder and one of attempted murder and has been remanded in custody to appear in the High Court at Christchurch on September 23.
* Ashburton Benevolent Trust has set up a fund for the victims, with support from the council.
Contributions can be made online or at any Westpac Bank branch - account name: The Ashburton Victims Fund. Account No: 03-0835-0342252-00.
