Parker signalled that head coach Neil Lennon was ready to move into the transfer market in January after a seven-match run without a win.
The former Nottingham Forest and Leicester midfielder stated after Wednesday’s home draw with St Mirren that some players were not turning up and performing.
And his patience is running thin ahead of today’s Premiership clash with Hamilton.
“The players know who they are and they need to improve,” said Parker. “I hope [they react positively to the comments] because I would if I was a player. It’s up to them, when they cross that white line they have got to put on a performance because the last few weeks they haven’t been doing it.
“I think it’s been taken on board but they have got to try a little bit harder, put a bit more effort in. They have to work as hard as they possibly can and, if they do that, other things will take shape.
“You can have a bad game but you have got to put as much work into it as possible.”
Striker Florian Kamberi was handed a personal warning after Parker stated on Wednesday he had to improve all aspects of his game after being hauled off in the 54th minute.
“It’s been a few weeks now that I’ve had a few things to say to Florian, and it’s about time now that he has turned it around and put in a performance,” Parker said. “We can’t keep waiting for him.”
Hibs beat Hamilton 6-0 two months ago to set up a chance to move top of the table against Celtic in their next game. But they have only taken three points out of a possible 21 since and have dropped to eighth.
When asked what has gone wrong, Parker said: “You have got to look at the players, when they go on to the pitch it’s down to them as well. Obviously we are going to take the blame.
“It’s disappointing because when we first came in, we got them out of the Championship and last year finished fourth, could have been second, the highest points, the crowds are coming back, probably playing the best football we have ever done. We started off OK this season and we are not doing it. And we’ve not done it.
“We need to get through this month and come January we need to recruit.”
When asked how these situations normally end in his experience, the 53-year-old said: “With a win. Just get three points and give everyone a lift.
“But we have waited long enough for this now, it needs to happen. Sooner rather than later.”
Hamilton have had a largely frustrating season so far and their manager, Martin Canning, says he wants some normality brought back.
The Accies boss is concerned by the severity of the Lanarkshire side’s defeats, with their most recent a 4-0 loss to fellow strugglers Dundee on Wednesday, when Canning says his players “were not doing their jobs properly” and were guilty of “switching off”.
Since that 6-0 thumping by Hibs in October, Hamilton have also lost 4-1 to Rangers, 3-0 to both Aberdeen and Celtic and 4-0 to St Johnstone.
“It has been a strange season up to this point,” said Canning. “When we have lost we have lost heavily. Last year we were competitive in pretty much every game we played in but this year we are either winning the game or we are not competing in the game well enough and that game at Hibs was a classic example.
“We need to get to the bottom of that and stop it.”