The two eldest sons of President-elect Donald Trump are coming under fire after details of an event planned for inauguration weekend have become public.

The Opening Day 2017 event would grant access to the newly sworn-in president for a lucky donor and 16 other guests - in exchange for a $1m (£808,000) donation.

The Center for Public Integrity found that these donations to unnamed "conservation" charities would allow donors a private reception with the new president, a "multi-day hunting and/or fishing excursion for four guests with Donald Trump Jr and/or Eric Trump, and team", tickets to other events and "autographed guitars by an Opening Day 2017 performer".

A brochure first made public by TMZ says that "all net proceeds from the Opening Day event will be donated to conservation charities," but does not specify which charities, or how net proceeds will be calculated. Encore Live CEO Walter Kinzie confirmed that his firm had been hired by the Opening Day Foundation to manage the event.

Opening Day Foundation documents list four directors: Donald Trump Jr, Eric Trump, Dallas investor Gentry Beach and Tom Hicks Jr, according to The Center for Public Integrity.

The event raises further concerns about the access that huge charitable donations will gain to the Trump administration, particularly if those donations lead to meetings with the Trump children.

"This is problematic on so many levels," Larry Noble, the general counsel for a nonpartisan campaign reform organisation, Campaign Legal Center, told the Center for Public Integrity.

"This is Donald Trump and the Trump family using a brand new organisation to raise $1m contributions for a vague goal of giving money to conservation charities, which seems a way of basically just selling influence and selling the ability to meet with the president," Noble continued.

Earlier in December, the Trump family tried to auction a coffee with Ivanka Trump for nearly $78,000 (£63,116). The auction was later pulled from the Charitybuzz website when ethical questions were raised by The New York Times.

After the Center for Public Integrity's report, a Trump transition official said that the registration document for the Opening Day Foundation would be "amended" and that the names of Trump's sons would be removed.

"The Opening Day event and details that have been reported are merely initial concepts that have not been approved or pursued by the Trump family," a statement from Trump's transition office said.

"Donald Trump Jr and Eric Trump are avid outdoorsmen and supporters of conservation efforts, which align with the goals of this event. However, they are not involved in any capacity."