Mrs Chadwick said it was hoped Parliament would let the council decide but there had been no clear indication that would happen.
"I meet Todd [McClay] on a six-weekly basis and thought he was getting the numbers. The law has been drafted but, obviously, he is struggling to get the law changed. I think we just need to keep the pressure on and it should be escalated by the Prime Minister [also the Minister of Tourism].
"After the [Northland] byelection, it's shown what can happen in the provinces and this can easily be done. We want to but we can't without the law."
In 2003 Mrs Chadwick, then a Labour MP, sponsored an Easter trading bill which was defeated by 63 votes to 55. In 2007 her second attempt with a Member's Bill was rejected by 64 votes to 57. Then in 2009 Mr McClay's Easter Sunday Local Choice Bill missed being passed by just two votes.
Mr McClay said "legwork" still needed to be done to gain support among MPs.
"One of the things that is really, really important is that there is no point having a debate if it fails. We have legislation drafted up and are in the process now of firming that up. I am quietly optimistic still that people will support this but we need to keep talking to them and put in the legwork.
"Rotorua is desperately in need of this and it is unfair that Taupo has it and we don't, during one of the busiest weekends of the year.
"It is frustrating but it's been 20 years since the law has been in place and we have to make sure we have numbers to get this right. I need to meet with Mayor Chadwick one last time for full agreement and then it will be appropriate to put it in the House in the coming months."
Retail New Zealand has criticised the "outdated laws", saying they need to be brought into the 21st century.
"Many New Zealanders want to be able to go shopping over the long Easter weekend - but at present many shops are banned from opening by Government regulation," chief executive Mark Johnston said.
"In 2015, when people can shop 24/7 over the internet, the regulations really don't make sense, and it's time they were reviewed."
The law gave some retailers an unfair advantage over others, Mr Johnston said, because "it's filled with exemptions that render it meaningless".
"A corner dairy can open, but not a supermarket. You can go shopping in Queenstown or Taupo, but not Wanaka or Rotorua. A shop can be filled with workers packing internet orders - but it can't open the front door to the public. None of these restrictions make sense in 2015."
Retail NZ would write to the Government asking for changes to the law, he said, with an aim of bringing in new legislation for Easter 2016.
"I'm not saying every shop must open, that everyone must shop, or that everyone must work - but if people want to, why should the Government get in the way?"
