Can't install debian because installer doesn't parse IP correctly?

I am trying to install debian on Virtual box using debian-7.8.0-amd64-netinst.iso When I insert my proxy server

http://192.168.2.2:3128

It says the installer failed to access the mirror. However on my host operating system (Ubuntu 14.04), with wireshark open, I can see the request is indeed going out and returning a list of hashes and gz files, so I believe I have virtual box configured correctly (using NAT mode).

When I switch into tty4 (which shows the error console), it says "Failed to fetch http://ift.tt/1xXGVM5 Cannot initiate the connection to 3128:80 (0.0.12.56). - connect (22: Invalid argument)

So I believe it is failing to parse the host portion of the proxy server and it thinks the port is the ip. Is my understanding correct?

I have also tried

export http_proxy="192.168.2.2:3128"
export https_proxy="192.168.2.2:3128"
export ftp_proxy="192.168.2.2:3128"

Other things I found was to add the proxy into /etc/apt/apt.conf, but as this is still at the installation stage, the apt directory doesn't exist.

How can I correctly specify my proxy?