More than a thousand NHS Grampian patients were treated in three central belt hospitals over a 12-month period.
Official figures showed 699 people were operated on at Ross Hall Hospital, a private facility in Glasgow, in 2013-14, up from 310 the year before.
A total of 235 people were treated in the Golden Jubilee National Hospital in Clydebank – an NHS facility – in 2013-14, up from 125 the year before.
Fernbrae Hospital in Dundee – a private facility – treated 152 people in 2013-14 and 127 in 2012-13.
Overall, 1,086 people were treated outwith the north-east in 2013-14, up from 562 the year before.
Labour MSP Richard Baker said it was “unacceptable that so many patients cannot be treated locally” and highlighted problems caused by NHS Grampian under-funding.
“This is a shocking rise in the number of patients being operated on outside Aberdeen and shows the true extent of the crisis faced at NHS Grampian,” he said.
An NHS Grampian spokeswoman said the figures related to patients, mostly treated privately, in order to meet a 12-week treatment time guarantee.
She added that the board was committed to fulfilling its obligations, but it was not always possible to do that so theatre slots were arranged for people elsewhere.
The spokeswoman said: “There are protocols in place which allow for referral to other centres – both NHS and private.
“We have invested £16million in new theatres at Woodend and ARI to improve our ability to treat patients, within waiting times.
“We expect this additional capacity to lead to a reduction in our use of the private sector.”
A spokesman for the Scottish Government said the amount spent by NHS Grampian in the independent sector to meet waiting time targets had fallen from £5.2million in 2012-13 to £4.1million in 2013-14, which equated to 0.55% of its total revenue budget.